Well the first build Archer2-Sapper2-Wugushi2-Musketeer is good for PvE, although I would do full str + maybe a little con, no dex. Yes crits are really good for Musketeer but most of your damage will be from Broom Trap and poisons which scale better with str since poisons cannot crit and at lvl 280 it takes around 7 crit rating to get 1% crit chance so its ends up being better to go str.
The second build Archer3-Scout1-Fletcher3, well the scout implies you want to PvP but Fletcher is more of a PvE build… If you want to PvP I would do Arch3-Scout3-Can1, I think the extended time on cloaking is very good, having a cloaking that lasts exactly as long as its cooldown, even less with server lagg, really limits your attacking window. Since in PvP because stone skin exists you are basically just running around in stealth waiting for the right moment to try to one shot somebody out of stealth. If your cloaking lasts 35 seconds and its cd is 35 seconds then your attack window is only in those last few seconds and that probably will not be the ideal time to strike. If you are not in stealth then you are not really going for kills but you are trying to either stay alive by running away or trying to cc with heavy shot or something else.
Another build for PvP is A2Rang3Scout1Can1, and with the recent nerf to bloodletting in Battle League there might even be some merit in taking Hunter or Quarrel Shooter for their stunning abilities. For any PvP build I would take at the very minimum A2-Scout1-Cannon/Musk1. What you do with the other 3 ranks is personal preference.
I think cannoneer is better than musketeer for PvP, and this is consistent with the top 100 rankings in kToS, if I recall correctly there was like 5-6 canoneers but only 1 musketeer. Cannoneer gets 60% block penetration which helps for hitting on high con builds, although its still stopped by stone skin. Plus canoneer’s big hitter is Cannon Blast which is AoE, if you manage to hit more than one target with it that is a game changer. Plus landing cannon blast may be easier than snipe because first you need to be able to see the buffs of your target the instant before you press the button to check for stone skin or reflect when you use snipe it’s a bit harder to check. Also snipe’s radius was nerfed and I have not played with it but I would image with how shitty the servers are sometimes you will aim directly at a target with snipe but then the server will not be synched with you client or something and the attack will miss, this would piss me off so much. A snipe crit or a cannon blast crit will both pretty much one shot anyone that isnt a high/full con build anyway so the extra damage of snipe doesn’t matter much. Plus canoneer gets siege burst which has a really long range, you can do off screen damage which is nice as well.