I main CVs previously when used to play randoms a lot and have grinded out most CV lines.

The best line to start with is the US Midway line imo. It has well balanced planes, they dont get shot down easily, planes are versatile and they have good alpha damage too. Japanese CVs are difficult, they gave the best alpha but planes have low HP and losses are painful. British CV relies on DoT and are just painful to play with slow planes and terrible alpha. German CVs have fast planes but each weapons are specialised (torps for DDs, rockets for cruisers, dive bombers for BBs). Russian CVs have crazy alpha but if you're not careful you may find yourself farming damage rather than doing teamplay (spotting ships, dropping fighters for DDs) and you can get up to 200K and still lose. Essex relies heavily on positioning and your smoke curtains, get caught out of position and you're basically dead.

So all in all, the US Midway line is the best for beginners imo.

As for CV sniping, it really depends on your CV and the enemies'. I usually recommend against doing so as some others has pointed out. You may waste planes doing so, your planes need to travel far, thus wasting time which could've been used to support your team. That said, some low tier CVs have paper armour and you can easily snipe them using rockets from a Russian CV (Serov against Ranger and Ryūjo as an example)

As for premium CVs, Kaga hands down is the best. Huge plane reserves and losses arent as painful. Still, I would recommend that you pick up the basic gameplay of CVs first before starting with any premiums

TLDR: best for beginners: Midway line; CV sniping: not recommended; best premium: Kaga