Yes, hit the blue button of your remote to show groups and navigate to the one you want. All the groups from your two providers will be listed there, provider 1 then provider 2 groups in the same list.

If your tv is android though I would highly recommend using tivimate instead.

Nope. You can only load one m3u at a time to siptv unless you use an m3u editor to combined the 2 playlists into one.

But I wouldn't recommend using siptv any way to watch iptv. Smart TV aren't that smart and arent meant to run iptv smoothly. Grab yourself a firestick 4k, install Tivimate, implayer, xciptv and see the difference. All these app support multiple playlists.