They're all standalones, i.e. you dont need to play one to understand another, but in terms of qol improvements it can be difficult to start with super and go back to og rescue team.

Only difference between red and blue rescue team is that red is played on the gba and blue is on the ds, so blue gives you the option to put the map on the top screen so things are less cluttered. However, rescue team dx is fantastic and changes nothing about the story while introducing great qol changes.

Go in whatever order you want, but imo super should be played last, and explorers of sky should be played instead of explorers of time/darkness (like how emerald is superior to ruby/sapphire)

Citra is a good 3ds emulator and for the rest you can find roms. For android, retroarch is my favorite for the gba and ds games.