I like upgrading objects by a slightly expensive over everytime I switch to a save, so that I get to try every new object in the existence

I like STARTING families, so I make a family, get them all jobs, take them through their first few promotions at work, then decide to start a new family. :-)

I usually do a aging system, and play rotationally, using the calendar mod I have it so after two in game weeks all Sims in the household will age up. For Adult sims I kill them and with Child Sims I use Gnohmon's Groot to give them the charm to age them up, the only problem is, that clothes and heads for aged up sims are randomised, so I save before aging up a child sim.

You can edit the Character file to give your aged-up child whichever head and clothes you want; see this post for how to do so.

Thanks. Now I don't have to exit the game and re-enter it a lot if times.

Probably just playing it regularly?
And taking advantage of debug cheat codes at a criminal amount