I can't help with Pandora or Retropie, but I do believe I have a workable solution for your heat issues.
I too have an RPi 4 and I immediately noticed that it ran warm. Actually, it idled warm and ran hot. I waited for firmware updates to appear and I installed heat sinks. The heat sinks lowered the idle temp, but had little effect on run temps. The early reports on the firmware changes sounded about the same. To measure you temps, take a look at https://www.raspberrypi.org/forums/viewtopic.php?t=34994
I ordered a fan shim from Pimoroni. The URL is https://shop.pimoroni.com/products/fan-shim. Shipping it from merry old England to Phoenix USA took quite a while, but when I installed the fan, run temperatures dropped a lot. I haven't used my new Pi all that much because I was concerned about the long term effects of running it hot, so my observations won't mean much. OTOH, there are detailed reports available that convinced me to purchase the fan shim. One is at: https://www.tomshardware.com/reviews/pimoroni-fan-shim-heatsink-raspberry-pi-4,6219.html.
The fan is very simple to install, assuming that you have the visual acuity and manual dexterity to handle some very, very small bolts - seriously small. There is software to manage the fan which is readily available and easy to install. I used the instructions for installing both the hardware and software at: https://learn.pimoroni.com/tutorial/sandyj/getting-started-with-fan-shim.
I'd buy this again. If it is available now from a US distributor, I'd do that rather than pine away for days waiting for it to arrive. BTW, I'm a spoiled Amazon Prime customer.