Bolts? Studs? ARP? OEM? I am confused

So I am slowly going to start piecing together parts for a build. Hp range 325-400 at the wheels so it'll be driveable on the streets. As we all know, when removing the head you need new hardware connecting the bottom end to the head as the stock hardware is Torque to Yield.

This is where my pea sized brain cannot comprehend what I need.
ARP offers 3 options if I am correct.

1.8T Head Bolt Kit
1.8t Head Stud Kit
1.8T Main Stud Kit

What the ****** heck are the differences. I know head studs and head bolts are what they say, literally either a bolt or a rod with a stud. But where does the Main Stud Kit come into play? What do I need it for?

I have read that some people just replace them with new OEM headbolts ( they take off the head, is this do-able for 400whp? Or should I just invest in new hardware by ARP?

Anything information is appreciated, even if it's just; S.Pellegrino, youre an idiot

I put the arp head bolts in and I think it was the arp main studs. I'd need to check my receipts on that.
I put the arp head bolts on because they are better than standard ones and incase the head needs to come of for some reason. Also thought it was piece of mind using the arp stuff.