Noise is usually caused by two factors: one inherent in the sensor size and the other in technique.
The smaller the sensor, and the more the MP count crammed into it, the smaller the Photosites: the light wells down which the light moves to be captured by the light-sensitive surface of the sensor. Smaller tubes mean less efficient light performance. That is why your 650D with an 18MP sensor behaved better in low light than the 32MP of the R7.
As a consequence, smaller sensors will be less efficient than larger sensors that have an equivalent number of photosites. When looking at the R7, which has a 1.6 crop factor, if one was to expand that pixel density to the size of a FF sensor, (32MP x Crop factor squared) it would be an 83MP sensor - which no camera maker has attempted in a 35mm format! I always thought that 20-24mp was a relative sweet spot for APS-C, as reflected in all of the other APS-C MILC models. If you look at the latest flagship cameras in the 1 series they have 24MP FF sensors which, if reduced to APS-C size, would have only about 9MP for that sensor area. That is one reason sports photographers want them - they are fantastic in low light.
Larger sensors will be more tolerant of under-exposure, which is not uncommon in light-starved environments, such as indoor sports. As Frank wisely said, using exposure compensation with a slight bias to over-expose to the plus side, might mitigate that to some degree.
As to the focusing. One challenge of the R7 body is a tendency to pulse if one is shooting a high frame rates. This is because the sensor on a MILC is used for focus (unlike a DSLR) and that mass of photosites sending focusing data cannot be throughput and processed by the focusing system in time. Thus, it will get one photo sharp, and the next one or two may be back or front focused. This can be mitigated to a limited extent by slowing down the shutter frame rate to 11-15 fps in first curtain shutter mode.
If you had the choice, and you really want the performance, I would suggest considering moving to the FF R6 or R6II which have the FF sensor of 20 and 24MP respectively, a higher-end focus and tracking system and significantly better tolerance to noise. The mechanical shutter (if you use that) is also much, much quieter.
