Attaching metal studwork to a drywall (not the other way around!)
I have used anchors in drywall /plasterboard for a wall on several occasions it really doesn’t take much with the bottom channel nailed down and the top attached to the ceiling joists.
If running parallel between 2 Joyce’s add nailers every 16” or so ( nailer a 2x4 horizontally between two Joyce’s 4” wide side down so you have a big target to screw into.
The wall joint is not really carrying any load but a couple anchors in the middle and a foot or 16” up and down would provide all the stability you would need.
If running electrical through the metal studs don’t forget to put grommets in if the cut out if it is not rolled. Recently had to open a wall because Romex (nmb) was used without grommets in a cold storage room the evaporator (cooling coil) fans vibrated enough to cut through the sheath and the insulation of the cable.
The 50 amp circuit was for the outside compressor, 50 amps of 120v made one heck of a mess on that stud and because they reset the breaker quite a few times it burned through the second hot the last time and welded #6 wire to the stud then they could no longer reset it and called me. (Very expensive repair).