What is the best gameplay method?

@Skellytoria    Hello! Apologies in advance, as this might be kind of a long post.  One of the best things about this game is there is no right or wrong way to play. It all depends on what you find enjoyable.  Personally, I like to start with one household and then play each generation as they come; i.e. sims get married, have babies, the kids grow, they move out, and so on.  I also like to have more control over what happens to my sims and what they're doing, so I have disabled aging, autonomy, Neighborhood Stories, NPC voting (Eco Lifestyle), and NPC relationship autonomy (High School Years).

Regardless of your settings, sims will not advance in careers or aspirations when you are not actively playing them. If you don't mind story progression, then perhaps try leaving the above settings enabled and see what happens.  You can also play around with the Neighborhood Stories options.  You can enable one, some or all of them.  As for autonomy, even when you have that disabled, your sims may sometimes do things autonomously even when you're actively playing them.  One example is when your sim is talking to another sim.  They may autonomously flirt or choose a mischief interaction, most often depending on their traits.  So that is something to be aware of as well.  Pay attention to the phone calls from non-played sims like "found a ring", "try for baby", "thinking of changing careers", etc. Your response to these will affect those sims' progression.

Something else you might consider is creating a save with all your sims and lots that you can load without having to start from scratch.  I did this and called it my "base game" save. I created and added multiple households.  I also added various lots as well as updated some of the premade lots to include lot traits.  This way, whenever I want to start over, I just load my "base game" that has all the households and lot changes.  Most of the time, I will create a new household, then use the "save as" feature to leave my "base game" intact.

You also mentioned switching households.  This is commonly referred to as rotational play, i.e. you rotate between households.  If you have Neighborhood Stories enabled, then your non-played sims may progress in some aspect and they can even die without your direct control.  Even when NS is disabled, some of your created but non-played sims may join a career that you did not choose and they will likely develop relationships (positive or negative).  The relationships will evolve whenever your active household visits a lot and your non-played household members interact with other NPCs.  Otherwise, without NS enabled (or depending on your response to the phone calls), your non-played sims are somewhat frozen until you play them again.

Lastly, if you are on PC or Mac and use mods, be aware that some mods can impact progression in ways that you may not want for your game. It's best to fully test mod features and understand all the settings so you know what could happen in the game.

Edit: I realize you did not mention mods in your post but I thought I should mention them just in case and for anyone else who might read this. :-)

Since you seem to have a number of saves, I suggest choosing one of them to add in all your created sims / lots and just try different things; maybe leave all the progression settings (aging, autonomy, NS options) and maybe try rotating between households.  I'm sure it won't take long for you to discover what appeals to you.  Hopefully this is helpful.  Happy Simming!  :-)