This flies so good the price doesn't matter.

This is definitely a budget build looking at some parts, with some clearance items, but as a test mule this makes me willing to push limits when tuning.

The budget magic here is a combination of comically cheap prices for decent parts, and not running anything extra beyond that.$165 all-in is a bit of a fluke price-wise, but anybody looking to get a top notch quad running on a budget should consider this overall build concept.

Motors came from all over for less than $12 each. I talk a fair bit of trash about expensive motors, but this build is a large part of why. This quad has inadvertently become my proof of concept that motors don't need to match - it currently sports one SzSpeed 2207, one Emax EcoV1 2207, one Eco2 2207, and one Amax Inno 2207 motor. 1900-1950KV works great, serving as a very flexible setup because this allows for 4S, 5S, and 6S batteries with some variations in propellers.
Frame is a Neutron-R. I prefer hybrid layouts, and it flies great with 5" arms out front and 6" arms out back, that little bit of extra weight helps me feel more confident in tight coordinated moves, and the visual excellence that is the MayDayFPV canopy just rounds out that frame as my favorite..
Stack is a HeliNation Talon F7 V2 with Spedix IS40. As a value proposition, for less than $60 this arguably the most gucci set of electronics I can think of for a race quad. F7 ease of use is phenomenal, and I know that ESC is ready to party on 4S/5S/6S with minimal changes to settings via the firmware (I run everything at 48kHz PWM, MedHigh timing, 0.25 rampup power, and demag comp on low). The overall tune is really straightforward, I run BF4.3 with sliders at: Master 0.9, PD Balance 1.2, P&D Gain 1.1, and FF 2.0, using DMinGain of 50 and DMinAdvance of 100. I run very aggressive DTerm DLPF filtering (biquad at 1.8 - this is aggressive, not recommended), otherwise running the tuning notes suggestions for dynamic notch and enabling yaw LPF.
FPV Gear is another budget set of choices. Foxeer's Predator Micro 1.7mm was $22 from RDQ, and is a brilliant camera. I've given up and stapped running budget cameras, because I can reliably get such good performance out of cheap builds that it's worth paying extra to see where I'm going, otherwise I find myself constantly 'outrunning my headlights'. The predator is still the best camera for racing, period.
The VTX is an AKK Race VTX, because $10 VTX does what I need it to. Finally, Foxeer Lollipop V3, again, on sale, but those are absolutely my favorite for ruggedness. The FC has a built-in VTX switch, making that entire thing easy.
Props are part of how I manage the very high KV - lower pitch is the answer. Gemfan 51433, HQ 5.1x3.6x3, and DAL T5040C props all work well on 6S setups. For 5S 1100mAh Black Series packs, this thing is a true animal. GF 51466 and TM5146 props are my favorite in that configuration. On 4S, I like the same 51466 props, and can use up my 51499 and DAL T5050C props as well.
Overall, the higher voltage lower pitch props give up a small amount of efficiency but return massive amounts of stability and performance in tight turns/moves providing much better lap to lap consistency. I find the sweet spot to be 5S on these motors as I can run them without any output limiting (cap transmitter at 94%, which allows the PID controller and mixer to still ask 100% power from a motor or two). On 6S, I limit to 82-86%, which is meaningfully more power on offer and probably contributes to the reduction in efficiency, but I am slightly faster and it feels more consistently locked in.
Batteries in this case are all CNHL units because price. The weight and performance of the black series is phenomenal, although I still use a lot of the older 100C G+ (White Series) packs because of insane value that I'm willing to punish them hard.

My best builds are not the planned builds

This just reacted to sales, an turned into the best flying quad I own.
I have probably spent too much money seeing just how cheaply I can build a good racing quadcopter, but can make the results consistently pretty good...
This partially breaks from that trend, because this is what I would build without any budget considerations. You can substitute frames (FlyFive33 SwitchbackPro Hybrid, or FPV FlightClub Neutron-R Hybrid StretchX are the other two favorite choices). Any other motor in the same size/KV range is going to perform brilliantly, and there are other ways to get the performance of this stack, but the Talon version is both the prettiest and best value in this case. Running nicer RC/FPV electronics at your discretion is nice - I'd keep the FPV gear no matter what, and if you want to run Tracer/Ghost/eLRS/CRSF that's awesome, but my XM+ running D16 8ch still turns in 9ms framerates perfectly consistently.
Short answer is that you'd be hard pressed to come up with a completey better build than this - but any substitution with nicer parts results in something slightly nicer.
My all-in price of $165 is a black friday fluke, and required buying other stuff to hit minimum order quantities to ship free. This ignores the price of consumables (props, batteries), and doesn't cover spares... but is still a comprehensively ridiculous price for something that can utterly outperform my ability to fly it at the limit.