Are there certain types of CO2/HPA tanks for each gun?

HPA tanks are the best to get. After you purchase yout marker and a great high end mask (as comfortability, safety, and visibility is the first thing you have to worry about), invest in an HPA tank. They have better consistancy, so you're gun will shoot the same direction most every time. It's much easier on your gun, as air is just...air. CO2 is a dirty gas and **** in your marker, making more maintanence on your gun and leaving you with fewer playing time=no fun. So first invest in a good mask, then HPA...this is a must if you want to keep on playing paintball(plus higher end guns will not work with CO2, and it's cheaper. Most fields will have you pay for each refill on CO2, but with air you pay like 5 bucks at most fields for all day air), and then get a better hopper to increase preformance and reduce paint breaks. After you get a good set of all these, then focus on getting a better gun or upgrades for your gun. Trust me, I would much rather use my JT Tac-5m Recon (basically the exact same as your Tippmann 98 pro custom) with a Dye Rotor(high end hopper), and an HPA carbon fiber tank, than my Planet Eclipse Geo(one of the highest end paintball guns), a gravity fed hopper(basically a container with a hole in the bottom and a place to feed it on the top) with a CO2 Tank.

yes, Some Guns recommend to Use HPA for it is much more safer do less damage to the gun. CO2 can break your o-rings and can also damage your gun. its best for you to use HPA for the Tippman 98.

i used to use CO2 and i have to change the tank o-rings a lot. CO2 makes o-rings freeze and cause a leak. So its best to use HPA.

same as above but one thing, hpa is highly recomended for electronic guns. co2 can be used on all mec guns.