Ahhhhhh... this is basically my job!
Small breeds are either companion breeds or terriers - either way they're generally sharp, need lots of exercise and mental stimulation, and may struggle without a person around. However whatever breed you get, bank on it being 2 years to go from puppy to reliable adult, and near that before you can routinely leave them for useful time frames without worrying about it or having to do lengthy set ups to ensure they're ok. You may well get there faster, but it is better to err on teh side of caution.
If you DO NOT LIKE fast clever loud yappy demanding dogs - do not get a poodle x. Just don't. Particularly, do not get a poodle x working cocker spaniel (as many cockerpoos are).
I would say half my day job is talking down people at their absolute limit with a cockerpoo.
Border terriers - neat, clean, tidy, one of the most trainable and biddable terriers, still a terrier though so fi you want unquestioning obedience without a seconds thought, not the dog for you. If you're happy to prove its worth doing as you ask almost every time you ask, fine, not a bother.
Whippets - lovely, typically very cuddly too, clever but less demanding than terriers on the whole. May have a high prey drive (so would a terrier) but they are a big fan of a comfy snooze too and typically not keen on going ou tin ALL weathers, just the nicer weather thanks.
Other ideas..
Grand Basset Griffon Vendeen (or the Petit version) - scent hound, so they can be a bit dodgy off lead but I've met plenty trained well enough to go off lead in places you already know.
VERY cuddly and affectionate, yet independent enough not to be super needy either. Food driven so easy to train, and their general attitude is that everyones lovely, but they don't HAVE to greet everyone, only those who acknowledge them (unlike some of the friendly breeds who can be a bit thuggish when young).
Cirneco D'ell Etna - whippety but more exotic.
Fauve de Bretagne - smaller than the GBGV and gingery.
Clumber spaniel - a big dog really on short legs but very steady, loving and patient unlike pretty much all the other spaniels!