The noise on the A51m R1 could get fairly loud, depending on the game or when doing video encoding. I will say that the GT77 fans get louder than the A51m R1, but I have as of yet to see any noticeable throttling on the GT77. I'll take louder fan noise over throttling any day. Frankly, the fan noise on the GT77 doesn't bother me, as I have the laptop tucked in under my TV and connected to the soundbar. I game in my living room on my OLED and soundbar, so I can turn up the volume if needed.
I have the fan on auto, so they will ramp up and down as needed, and I find that they do a good job of anticipating when to go up or down. But, if I wasn't gaming on my TV and soundbar, I'd use a good set of earbuds or headphones, because don't think the volume of the laptop speakers would be enough to drown out the fans.
For me, it is finally nice to have a system that handles everything I throw at it with room to spare. Another thing that bothered me about the A51m R1 is that Dell put in a I9-9900K and a GTX 2080, but capped the RAM speed at 2400Mhz. You could buy faster RAM, but it would clock down to 2400Mhz. That RAM speed was unacceptable even for the time when the laptop was released. The A51m R1 was designed and developed with almost no room for thermals, so I guess they figured they could give some thermal headroom by clocking down the RAM. This was even more obvious when they started dropping BIOS updates that purposely throttled at ridiculous levels. And folks that bought the A51m R1 after they started BIOS throttling were in for a big surprise, since Dell didn't disclose this throttling when selling the laptop. They knew they had a problem...