The number of resources do not increase with the player count on that server.
Resourches have a fixed placed where they spawn, but do spawn at random locations in that area. There are plenty of resourches to be found on the map, get to know those places and make sure you gather everything before anyone else does, the resourches spawn about 2-3 every INGAME day. so if you see a place that hasnt got any resources, but it did have resources a few minutes ago watch ur back, because someone might be nearby
Yes there are a few Rad towns on the map, but not all good loot come from rad towns. There are some soort of bunkers along the road with low radiation levels and they also have 1 or 2 chests you can loot from.
inside chests you can find Anti radiation pills which will lower your radation level once you consume them, very usefull and not rare to find.
also you can get anti radiation clothes which can be crafted on your own when you research them using a research kit and some paper while standing close to a workbench. They will decrease the amounth of radiation you get alot.
Kevlar armor also provides a good amount of radiation protection, using this type of armor with anti radiation pills and you can loot all day.
Remember once your radiation level exeeds 500 you will recive damage, not alot but i will kill you eventually.