My steel/vinyl pool is over 30 years old now. I have had to replace the liner twice due to age (so, ~10yrs per liner). I believe, most steps are fiberglass - mine are, and are original.
A gas heater is the most efficient - if you have a reasonable way to run the gas line. Water sucks a LOT of heat to warm up, so no matter what heater, be prepared for much, much higher energy bills. I only use mine a few days in the spring, and again a couple of days in the fall. A heater can be a "do it later" option if you want to hold down initial expenses.
A "bubble wrap" type solar cover can go a long way toward heating and retaining heat, just from the sun. Explore options, mine uses a manual reel to take it off, and it is a bother to cover/uncover each time the pool is to be used. Not too expensive, and can be added any time. There may be more modern arrangements than mine. An autocover is neat, but may drive your budget too high. It does need to be installed during the build.
Lots of debate about off season covers - I use a mesh type that can even be walked on, to keep the pool area safe during the winter. Others like solid covers, that are not walkable but do a better job of keeping dirt out.
BUT - the best, most important thing: Get a Variable Speed pump, and a Salt Water Chlorine Generator. This is a must. You'll otherwise go nuts managing the chemistry - it will be like adopting a puppy and needing to buy expensive food and feed it every single day. No exceptions. But, with the generator, the work load shrinks dramatically. I only need to check mine weekly, and it only takes 15 min.
The variable speed pump allows you to save massive amounts of electricity. Most of us run them as slow as we can 24/7.
Walk away from your builder if they try to scare you about rust and corrosion with a salt pool. The salt level is 1/10th the ocean, and most can't even taste it.