I have floated many rivers in pontoon boats, as well as in drift boats. It is quite possible to fight and land fish while floating rivers, and I do it all of the time. Drift boats are obviously preferable, in my opinion, but pontoons also work reasonably well.

I wear and use good flippers to control my float while fishing, as well as often using one oar to help control the pontoon while casting with the rod in my other hand. The same goes while playing any fish I hook while floating. I also beach the pontoon, get out and wade fish from shore, as well as trying to get to shore to land fish, where practical.

It helps a lot in landling size able fish from a pontoon to have a good, long handled net.

There are some disadvantages to using pontoons. First, it can be difficult to slow the boat in faster moving water, and you might float right past good water before having a chance to fish it, or fish it as thoroughly as you could while wading. If you hook a fish when floating in faster moving water, it can also be difficult to play and land a big fish while you are floating downstream. Also, you have to be very careful when anchoring your pontoon in rivers - because of the danger of anchoring them in moving water, I ordinarily only use my anchor to secure my boat at the shoreline.

I spend my summers on the Yellowstone River in Montana, and particularly earlier in the year I use my pontoon to float a 4 mile section of the river in the evening, right up until dark. (Okay, sometimes after dark, according to my wife!) I also have a drift boat, but it is easy to put the pontoon in and take it put where I can't do so with my bigger boat, and it can be quite relaxing just to float along in the pontoon.