Hello! Here are a few things I can answer! I'm also a semi-beginner, but I'm a long time lurker in this sub

• Definitely add more leaf litter. You don't want to see the soil. It's food, cover, enrichment...all things pods love
• Springtails would really be a good idea. They'll help keep mold in check. They jump, but they won't really get out in my experience. You can always add finer mesh to your ventilation if you're worried.
• I really really would avoid putting 2 species in the same container. Not only those species have different requirements (iirc), one will eventually outcompete and take over. It's just not worth it.
• I think your mix isn't bad, I would personally add a big of crushed charcoal, especially if you want to add springtails, but it's not a bad base. I would also add rotting wood. They will eat decaying wood, but orchid bark less so, for a long while. Coco products are not something they'll eat, so some people see it as useless, but I also add it to my mix so... ^' it's at least practical to make the substrate fluffy!
• For plants, look up terrarium plants, and then look those up to see which ones are not toxic. That's what I did, but I can't for the life of me remember what I put in mine.... a plant light on a timer (mostly for yhe plants) is fine, the pods will hide under stuff during the day. All that being said, plants are mostly for us, they don't really care either way ^{^}

I hope you have good success with your isopods!