I do a lot of small terraced houses that're compact, and I have a couple of days doing fairly large houses in the countryside.
I prefer the large houses in the countryside, as they're better priced and I find them easier to do, but I still also like my terraced houses; we can knock each one out quick and the ones I have are mostly retired types that've bought their council house and go out of their way to make sure I'm paid; even paying for their neighbors who aren't in.
As for collecting, I collect on a Saturday morning on my compact work, but for my 'drive betweens', I leave a SAE with payment instructions after I clean.
So I use a mix of envelopes and trad collecting.