Best practices? every tick vs. every 0.x seconds vs. dt

So, I am getting started with the platform, and I want to settle in a good model to update the game state.

I can do 'every 0.016 seconds' for a theoretical 60 game state updates per second.

Or I can to 'every tick' - which I don't know how to set the tick rate.

I can also use dt to track how much time has passed since the last game update, but I suspect it is tied to tick rate, so I don't know if it would interact well with 'every X seconds'.

Both tick rate and 'every X seconds' are a best-effort, that is limited to processing capacity of course, so the game will slow down if there is too much going on.

Are there clear downsides on using 'every X seconds' over 'every tick'?

Can I set a fixed tick rate, or cap it at e.g. 60 hertz?

I would like to have game logic to run at a fixed rate independent of frame rate, even if frame rate slows down. Would it be a good model to use 'every X seconds' to update data, and use 'every tick'to update the screen?

Yes, making the 'Every X Seconds' updating data can be better and will not outrun the memory of the game, and, the 'Every Tick' will literally at every 1 tick updates the game screen, but, you can do it with the 'Every X Seconds' for better Ram memory. Normally i use the 'Every X Seconds' to minify the use of the Ram, specially when i'm making an bigger game. But, you can normally do with boths, the only change is that will affect the game's perfomance.