Fallout 1 and Fallout 2 take precedence over Fallout 3. This means:
Power Armor is the top of the heap! Power Armor is the ultimate armor. With it, you will be stronger, tougher and better protected from the elements than anyone not in power armor. This also means that if you run into anyone in Power Armor (Brotherhood Paladins, and no one else), you will receice a well-deserved ass-whupping if you start a fight. Most bullets will ping helplessly off Power Armor and those that don't will dent the surface, scratch the paint and fall to the ground in a mangled blob of lead that used to be a slug.
Energy Weapons are powerful pieces of gear! So what if a shotgun is better than a Laser Rifle in Fallout 3? The roles were reversed in Fallout 1 and 2. A laser rifle will happily burn holes through everything short of Power Armor and nicely cook the little guy inside.
Super Mutants are your worst nightmare! Title says it all. In Fallout 1 and 2, Super Mutants were among the most intimidating and dangerous opponents you would face. In small groups, they are quite capable of killing your followers and beating several shades of black and blue into and out of you. So don't go around killing them off left, right and centre. In a straight-up fight, unless you're in Power Armor, Super Mutants will rip your shit without missing a beat.
Getting shot is a big deal! I can't stress this enough. Getting shot hurts. And that's when it doesn't kill you straight off the bat. Sure, in games and films people get shot and still kill the bad guys and get the girl. We're trying to be a little more realistic. Shooting an un-Power Armored human will severely injure them, if not kill them. Super Mutants and Power Armored folk can take a hell of a lot more punishment, but until such time as your character becomes one of those things, please treat an injection of lead appropriately.