Wingman is great, but heavily depends on your ability to aim. Not much room for error and can be punishing if you consistently miss. Risk vs reward.
R301 has been my go-to rifle lately, and is great even with no attachment. Incredibly accurate, hardly any spread, light ammo is plentiful, and the fire rate is in a great spot. Get it fully kitted and you're setting yourself up for a smooth victory.
Don't have any faith in hemlock or flatline, I only ever use them until I find a replacement. Flatline's recoil isn't worth having for the small increase in damage compared to the R301, and have just found both of these rifles to be unreliable most of the time. I'm sure if I used them more I might grow to like them, but as it stands, not for me.
Have yet to use the prowler with select fire mod extensively, as it is complete garbage without it. Seems like a lot of top streamers are siding on using it with the attachment so it could very well be worth investigating. Check it out!
Peacekeeper is a given for close range, and if you have the precision choke, it can easily be used for medium-ish range if you charge it up. There's no real reason to run anything else as a secondary compared to the peacekeeper, unless you are using a sniper. Peacekeeper is just too good in close range to pass up IMO.
Have recently started using the spitfire quite a bit, but still find myself choosing the R301 if it were to come down to choosing between the two. I've found it to be a solid weapon though and would recommend it over the other heavy ammo rifles.