Ok, for detail work this is a good dremel kit. It’s their most powerful dremel. Get a Flex shaft extension too, sells for 29.95 Amazon. Some of the supplied bits will get you started. You can add on other bits as you need them. I use this tool alot, not just for trees.
Dremel 4300-5/40 High Performance Rotary Tool Kit with LED Light- 5 Attachments & 40 Accessories- Engraver, Sander, and Polisher- Perfect for Grinding, Cutting, Wood Carving, Sanding, and Engraving
I don’t use die grinder often and have used a number of them…. For heavier work Makita has a decent powered 1/4” die grinder for a decent price on Amazon. Be aware you can get some pretty pricey dir grinders and some cheap Chinese knockoffs too.
BlueMakita GD0601 1/4" Die Grinder, with AC/DC Switch, Blue
Bits are a whole another deal. A popular bit for bonsai is sold by Bonsai4me called the Nibbler. There a couple sizes. You can also get these for Dremels. They are pricey but do a good job.
Cheers
DSD sends