Whether you will like using a fountain pen depends on a number of factors. Obviously, how well the pen writes is very important. But fountain pens write very differently from other types of pens, and that difference is something that takes getting used to. In addition, fountain pens require active maintenance, and can be messy both to use and to maintain. Some people never become comfortable with fountain pens. It's not the pen, but rather whether the user enjoys the overall experience.
The keys to whether a fountain pen writes well are the nib and feed - the components that control the flow of ink. Now, there is an element of 'different strokes for different folks' in that some people prefer a dry pen while others prefer a wet pen - in the world of fountain pens, 'wet' and 'dry' refer to how much ink the pen lays down on the paper. In my opinion, wet pens are generally easier to use, but can be a bit messy because it takes time for ink to dry, and if you touch the written page before the ink dries - - -
Another factor here is the size and style of the nib. Nibs range from 'ultra extra fine' to 'broad' - most kits come with middle of the road 'medium' nibs. That's a good starting point. There are also specialty grinds - italics, stubs, etc. Leave those for advanced users.
Most pens, and most pen kits, use plastic feeds, that there isn't much that can be done about a plastic feed - it is what it is. There are pens where the feed is made from a hard rubber compound that can be 'tinkered with' using heat, but that's usually something for advanced users. However, nibs can be 'tuned' to improve their performance. Tuning involved adjusting the spacing between tines of the nib to achieve the desired ink flow, and polishing the tip to minimize scratchiness. Expensive factory-made pens are often tuned at the factory, but that isn't practical on less expensive pens and components of pen kits. So there is an element of chance involved when you first use a fountain pen made from a kit.
I am a fountain pen user, and have several kit pens in my every-day-carry rotation. None were expensive kits, and they all write well. I have polished the nibs a bit (polishing is simple - actually, paper is mildly abrasive and simply writing with a pen will eventually polish the nib). Attempting to adjust the tines of a nib is a more advanced skill that requires time and practice to master.
There are, however, two factors that I think are important in choosing pen kits. The first is how the cap connects with the body - I prefer pens with a screw on cap because that design is more secure and minimizes the tendency for the nib and feed to dry out between uses, but I admit that most of the pens in my EDC rotation are the alternate snap cap design. The other factor is whether there is a center band. This is purely a matter of esthetics - if there is no center band, then the end grain of the wood used to make the cap is visible when the cap is removed. I don't find that very attractive.
You mention pumps - in general, the decision between various pumps, and between pumps and cartridges comes down to convenience rather than how well the pen writes.