After watching hours and hours of Rotor Riot and Joshua Bardwell videos on YouTube while stuck to the couch with COVID, I decided to leap both feet first into FPV several months ago!
This is the build I came up with, and it hasn't been without its issues, but it flies so well with minimal tuning beyond dynamic filtering.

It weighs 338.7g without the battery, or 695.9g with a 1200mAh 6S and GoPro Hero 3+ in the full housing.

When the parts first arrived, the TMotor Velox F411 FC was dead on arrival, so I got some solder practice in by re-mounting everything to the new FC, which RDQ graciously warrantied for me after I documented what happened.
After that, two FrSky Archer receivers bricked, and I thought it might have been the BEC, but the new R-XSR has been phenomenal.

Once I got those parts installed and the quad flew, it's just kept flying!
One RX Loss failsafe caused it to smack the ground pretty hard (my fault) and broke my GoPro, the VTx antenna, and fried the VTx.
I upgraded to a Foxeer Pagoda Pro VTx antenna, and just replaced the Xilo Stax VTx with another one.
I also flashed the Velox ESC with Bluejay firmware to add RPM filtering and a custom POST tone.
My initial prop selection, the Gemfan 5130 Freestyle 3S, flew well, but felt lacking in power. I switched to a slightly more aggressive pitch with the Vannystyle 5136s, and it seems to be a nice sweet spot between flight time (~7 min of cruising and light open air play from a CNHL 1200mAh 6S) and power.

The Source Two frame has been nice, and the quad is incredibly light. It doesn't carry much momentum, but that's fine with me, as it's more of a 5" cruiser than a super high performance freestyler for now.
I had some resonance issues I tried to tune out, however, and the nee0 TBS Source Two GoPro Universal Mount has introduced weird 60hz oscillations when carrying a GoPro, so I designed a new one.
I highly recommend running the Source Two with a bottom battery, when I ran it top-battery, I was dangerously close to a prop strike on my battery lead at all times, just due to how the frame and motors sit.

Would I pick these parts again?
Probably. They're cheap without being shoddy, and the quad has taken several crashes without too many issues!
If I had to change parts, probably a 32-bit ESC and ExpressLRS receiver.

WATCH IT FLY!