Bonsai Nursery - Thoughts

I am planning to build a bonsai nursery and wanted some thoughts from the experts.

Will be using a raised garden back in my backyard, shaded by the maple tree that birthed all these little saplings and a honey locust. I will be transplanting them from my landscaping where they have been popping up into a soil mix of my existing soil, leaf mulch, pine bark mulch, and pumice. I know this would have been more ideal timing a month ago but I had surgery and could not garden, the saplings look strong so I hope they will survive.

I have plans to overwinter them but wanted some of your thoughts too. I did try this last year, only winter protection was leaf mulch on top, and the wind and cold kill all but 2 (and they got beat up still).

But I am curious about how much I should prune if at all, if frost cloth will be enough for overwintering, how long I should wait to style, any tips to speed up trunk thickening, or anything else you can think of. I am likely missing a lot as a newb. But my zone makes it hard to keep bonsai outside year round so I am hoping a local tree variety and a dozen+ specimens will have more likelihood of success.

Thanks y’all! Really love this community.