Still kindof a nub myself, but I'll give it a try:

It always depends on what you're trying to achieve.

If you just want to hold your keys and need a channel only to zap and be zapped, small channels are ok, maybe even make them private, so you're the only one using them.

(Lightning-)Fees don't really matter on private channels, I'd do a small zero-fee channel with you if you need one, just gimme a hint.

If you want to route other peoples Tx, bigger is always better, in terms of network-liquidity and fee-settings.

example szenario:

you open a channel for 99sats and assume you might be able to close it for another 200sats.

You'd set the fee of a 1M channel to 300ppm, so if the channel just gets drained, you don't lose money.

For a 10M channel your low-risk-fee-limit would only be 30ppm though, which means cheaper Tx (and better liquidity) for everyone.

And for the sooner rather than later question, that's just a matter of the mempool/on-chain-fees really. Everytime the fees are low is a good time to open (or close) channels, no matter the size, now or someday.