@stu929 sorry, I've been on the road, out of touch for the last few weeks.
For What It is Worth - Pretty much ALL spruce follow the same growth patterns, pretty much ALL respond proportionately to pruning. Meaning large needle spruces like Picea pugens reduce the same relative percentage as small needle spruces like Picea orientalis, meaning you won't get tiny needles on pungens but you can get a 50% reduction on pungens. Pungens = Colorado Blue Spruce in "American vernacular". And when the already relatively short needles of Picea orientalis "Oriental Spruce" actually from Turkey thru eastern Caucus Mountains, reduce from their already short 1/2 inch length, you can get some nice short needles. The same techniques outlined for Jezo spruce, and other Japanese spruce can be applied to pretty much all spruces. The biggest differences between the different spruce species is needle size and heat tolerance for growing conditions.
Some, many spruce species are montane species and do not tolerate high summer temperatures. In particular high night time temperatures in summer can kill montane species. They must cool off at night. This is the reason you do not see spruce in Louisiana, Mississippi or Alabama. The northern Japanese species like Picea glehnii simply do not do well at low elevation midwest and southeastern USA summers, just too hot at night.
But many spruce, Picea, come from middle and lower altidudes in middle latitudes and do indeed survive Midwestern summers at low and moderate elevation. Some are high elevation trees in their native ranges, but survive well in low elevation, for example Picea pungens, and others are native to low elevations. (I need to check for books for specific examples, but I am sure they exist).
For all spruces I have generally done most of my work in late summer. The timing in the Chicago-Milwaukee area is about the 3rd week in August, late summer, the current years new buds will be visible and formed in preparation for next year. Usually half way along the current years growth you will see dormant buds that have been developed. If you are going to prune back, at this time through into autumn you can prune back to these dormant buds, they will sprout the following spring. After pruning you can then wire out the tree. Spruce is flexible, branches often have to be wired repeatedly for many years to get the desired change of direction. Remove wire in spring or early summer, before it cuts into the rapidly expanding branch and bark.
Personally I tend to repot spruce in late August, in my mild summer climate this works well for me. If you are in a different climate than my "Lake Effect" Great Lakes moderated mild summer climate, do your repotting in spring. For most of the country repotting in spring will probably work best. Generally spruce are very winter hardy. Most are zone 5 or colder hardy, and for most of the lower 48 states their pots can simply be set on the ground for the winter if they were not freshly repotted. Cold and windy normally does not bother them. If they are freshly repotted a shelter from wind and deep cold is a good idea. Shelter from the wind is more important than shelter from cold temperatures. In general spruce require at least half day of direct sun, and most do better with a full day of direct sun. In the south, where summer sun is particularly hot, shade cloth is recommended. In the north, no shade cloth needed.
Again care for all spruce species is pretty much the same when it comes to timing of pruning. Biggest care differences are the extra care required to limp montane species through hot summers.
For "normal humans" living with Midwestern and southeastern USA, hot summers I recommend experimenting with Picea orientalis, the Oriental spruce or Caucasian spruce. The reason is that it is well adapted to a dry, low humidity summer climate being from Turkey and the Caucus Mountains. I had one for a fair number of years, the needles are very short, a nice very dark green, almost black from a distance. The needles are every bit as short as any of the Japanese spruce. The Milwaukee Bonsai Foundation collection housed at Lynden Botanic garden has a 70+ year old Picea orientalis that has been grown as bonsai for at least 40, maybe 50 years. It has a good track record as bonsai. It tolerates warm midwestern summers. This spruce will thrive where it is too hot and dry for P. glehnii and Jezo spruce.
Any of the spruce species, as normal wild type forms of the species make decent bonsai. Our eastern half of North America native Picea glauca, the "White Spruce" is no exception. The normal form of this species makes a nice bonsai. There is a geographic race of the white spruce, Picea glauca densata, known as the "Black Hills Spruce" which is particularly good for bonsai. Andy Smith of Broken Arrow bonsai has distributed many excellent collected specimens of the Black Hills spruce. Look for Black Hills Spruce if you are looking for a hardy spruce to get to know spruce.
However there is a horticultural atrocity of a cultivar of P. glauca known as 'Dwarf Alberta Spruce'. Please do yourself a favor and avoid attempting bonsai with 'Dwarf Alberta Spruce' at all cost. This genetic mutant does not harden its wood properly, branches remain forever juvenile, and will reach for the sky no matter how many years of wiring you have done to try and keep them down in shape. DAS is a plague on bonsai-kind and should be burned, chopped and composted when ever possible. Unfortunately DAS propagates easily, even from cuttings, so you see it in landscape nurseries everywhere. Avoid it if possible.
Most spruce can only be produced in commercial quantities by seed or by grafting. So generally unnamed clones of species from seed will be the most common, and for desirable landscape spruces grafted clones will be available at the appropriate price mark up. Colorado blue spruce have been line bred to produce gray colored trees from seed populations. The really bright blue Colorado blue spruces are all grafted. Grafted plants can be used for bonsai, a graft is not a "fatal flaw", if the graft is well healed and not obtrusive, the grafted tree is perfectly fine for bonsai. However a badly matched graft is a "fatal flaw" so if you choose to work with grafted material, spend time evaluating the quality of the graft of the potential bonsai before you begin investing the time and effort.
Picea omorika, the Serbian spruce, was asked about. I've had one for only a couple years, it got left behind when I sold the farm. I really liked it. Shorter needles than Picea glauca, and Black Hills Spruce, needles slightly longer than Picea orientalis and Picea glehnii. It seemed to be a good spruce well adapted for Michigan and Illinois summers and perfectly hardy for their winters.
So that pretty much exhausts everything I know about spruce.
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