All of the pagids I've seen are just a flat surface rather than grooved or anything. Would you say they're good enough and buying more expensive ones would be overkill for what I'm going to be using them for or if I can afford better ones then get better ones? I Don't want to waste my money but I don't want to cheap out either
Flat faced are absolutely fine, drilled and grooved are not needed unless you're going to track it and your brakes are cooking or you're trying to save weight. All they'll do is wear your pads faster and potentially crack.
Machanic said it would be fine to drive home as the discs are made to get rid of heat, something like that. 

Yep, brakes are designed to get f**king hot due to being seized and be absolutely fine. Not.
I've seen a seized caliper feck brake pads, discs, grease seals and a bearing all in one hit. The brake disc was blue and seriously, seriously cracked.
The van had about 3 tonne on it most days too.

Brakes, don't feck about with them.