Ask about rebar (prefer #4 in Texas), structural warranty (lifetime transferable in case you sale your home). If they stand behind a solid structure you can be fairly confident. Equipment is really all up to you but make sure there are 2 drains and plenty of returns for good water circulation. Lastly, plaster, pebble, quartz, etc. Look into your finish and desired water color. Then look again and again. The builder may even have pools you can go look at. Finish/Plaster is probably the single most important thing to obsess over.