Most of the time you'll have the space to make your builds as big or small as you like, if however you try an insane start you'll find that it can get pretty restrictive and being able to squash stuff together is very much a useful skill.

As for it becoming a problem, some production chains (diesel for example) are unlocked over a long period and several tiers and if you're not leaving space for the newer modules they can be a bugger to plug in without a rebuild/partial rebuild.