Everyone has their own opinions, but I think most will agree that you can't go too wrong with a Neu based motor. Obviously and actual Neu is good, I run one of the Blue can that were made for Tekno. The Castle 1/8 motors and the Tekin Buggy an dTruggy motors are also Neu designed, and add sensors for the totally smooth start up.
Choosing the KV is fairly easy. You want to target a motor RPM around 30,000 with 25,000 to 40,000 being usable in many chassis, but watch the gearing range of your s to make sure you can gear down to 30 mph and up to 40 mph, that should cover any normal track. So if you are on 3S, a KV from 2200 to 35,000. On 4S the range goes from 1700 to 2700, on 5S 1350 to 2100, and on 6S 1150 to 1800. This is a wider range than most recomend, because I am trying to cover all possible gearing options in cars. Obviously if you can't gear slow enough, 40,000 rpm is useless. And if you need a 25 tooth pinion, then 25,000 rpm may be too slow as well. You also want a motor rated for over 700 watts at your chosen voltage, or it will run hot in racing. I like a 1,000 watt or higher motor for some safety margin.
The Tekin RX8 does sound like a great ESC on specs and features, but I have never run one. The Mamba Monster V3 is a brick, it will withstand just about anything you throw at it, and keep cranking out power. It is a sensorless only, but that is not a problem in 1/8, the 4 pole motors run very nicely on sensorless. I was running an original 1/10 Mamba Max on 4S into a Neu 1512 2050 for a long timr with no issues at all. I started having glitches so I switched to a Mamba Max Pro, only ti find out the glitching was caused by my steering servo. I am currently still running the MMPro with great results, even in sensorless only. The fact it will run sensored can be an advantage on very tight tracks, if you get a Tekin motor. I may switch back to the old Mamba Max as it ran about the same, and it would free up the MMPro for me to use in my 1/10 with a sensored spec motor. The only real issue with the old MM is that it needs an external BEC to run anything over 3S, in fact, even at 3S I would use one as the linear BEC add heat to the ESC. It is also limited to 4S by the voltage of the internal components. But I never plan to run any more than 4S as it is more power than you can use on almost any track. The only reason for 6S in my opinion is to get real long run times.