To get the hang of aiming manual shooting you can hold L2 to bring up the aiming line. If anything, manual shots are far more effective than basic/advanced once you get used to it as they have so little/zero error and fly like a rocket. Even the e-sports players use them most of the time and they usually use all assistances available.
From your camera angle though, I'm not so sure I'd ever be able to get used to manual controls

One thing I do like on manual shooting is the headers, they seem to have more power and divert the momentum of the ball. That combined with the freedom manual crossing gives can lead to some nice goals, it's my most satisfying way to score in this PES. Another thing linked to which which works nicely on manual is using L1+

lofted through ball as a cross, either low/medium power from the byline or full power from further away, you really have a lot of options from out wide on manual.