Are these runs supposed to be set to easy game and combat difficulty? Please someone tell me

It's not needed, but logically speaking, it's the fastest. I'm not a total fan of it as it takes away the difficulty(/competition) factor, but still, aiming for the easier skillchecks (vide Fallout 1: science, speech and lockpick) typically means a faster run.

On a side note, you may want to post in the dedicated forums for the precise games of the series and not here. If it's Fallout 1 I could help a bit. You may want to contact DrTChops for access to Fallout Discord, too.

BTW, congratz on finishing Prince of Persia 1 in such a nice time! (tho I've watched Capn's run first, but still it's an achievement, and it was the very first game I played on PC, so I'm fond of it : )