Should I open fewer and larger channels or rather more smaller ones?

It's generally better to open fewer larger channels. If you have 5M, open two channels within a swap with others: a 3M and a 2M channel. This way you will have 4 channels in total. This way you will have redundancy for both sending and receiving funds.

You can also save some of your SATs to open dedicated channels to services you use often. For example, if you use Bitrefill to buy gift cards or phone top-ups often, it makes sense to open a channel to them directly so you can send SATs fast and without paying routing fees to any routing node.

If you have excess funds, you should also consider joining Swaps with node operators who want to open smaller channels to help connectivity and potentially earn routing fees.

I've read that to be considered a "good peer," the calculation only accounts for channels over 2M. So, depending on the amount of sats you have on your node, I'd consider opening channels for no less than 2M per channel. This also presupposes you are attempting to be a routing node...