No question is neophyte
First, on roles: there are definite roles that teams must fill in order to be successful. Besides the ‘in game leader’/IGL (read: quarterback), you need an ‘AWPer’ who is primarily good with scoped single-shot rifles, an ‘entry fragger’ who is primarily good with the automatic rifles and is just a naturally good aimer, and you need a ‘support’ who is primarily good at setting up plays with well-thrown grenades. At the professional level, most all players are good in any role, but are just fractionally better at one aspect than 99.9% of the player base, and it makes all the difference.
Regarding shot placement and accuracy tracking, that’s a bit of an open question. We’re just beginning to work on how best to collect and use such data on our platform. There’s the potential for a lot of noise in such statistics as not all shots taken are necessarily at a known target; an attacker may ‘prefire’ around a corner having already lined themselves up towards a known common defensive position in an attempt to mitigate a stationary defender’s advantage without there being anybody there, or just pummel a permeable wall (commonly known as ‘spam spots’) playing the odds there might be someone on the other side that catches some damage, or just garden variety suppressing fire. All things that can pull a basic accuracy stat out of alignment. We might have some ways of filtering out these noisy cases, but just hypotheses right now.
Generally speaking, weapon choice in any given round is dictated most by how the game is balanced and the team’s economic situation in the round. The ‘holy triad’ of AWP-M4-AK has basically dominated CS since the beginning, and most weapons are underpowered to the point they barely if ever show up in competitive play. Typically if an odd weapon becomes in vogue for a time, it’s due to an inadvertent change on the developer’s part, usually some bug fix having an unintended side effect, so is hot for a couple months until it’s patched back over. If a team’s economy dictates that they need to empty their accounts and buy whatever they can get, because they need to win a round to stay comfortably in a match, then players will typically have a personal preference of what they buy in such situations, regardless of relative efficacy vs rifles.