Builder's warranty is only for one year anyway, and many of the upgrades homeowners do with outside contractors does not void that warranty. It really depends on the upgrades.
Thing like shower tiles, tub surround, should be done through the builder. It actually cost more and very messy do it afterward. If the 3red party contractor didn't do it right and caused a leak, you are on the hook for repair bill. If there's a leak that is caused by the builder but you have 3rd party do the tile work, builder can denied the repair since there's work done by others and it's hard to prove who cause the damage.
Thing like shower tiles, tub surround, should be done through the builder. It actually cost more and very messy do it afterward. If the 3red party contractor didn't do it right and caused a leak, you are on the hook for repair bill. If there's a leak that is caused by the builder but you have 3rd party do the tile work, builder can denied the repair since there's work done by others and it's hard to prove who cause the damage.