The maximum maya will do on most display cards is 4k*4k on viewports it does not mean they dont render that high (provided they dont ilter anyway) its just the maximum you can allocate for your viewports (on some cards maya odnt permit higher than 2k and on some it permits 8k). Also DONT use jpegs as your textures its a bit stupid, even if they save space on disk they DO NOT SAVE SPACE on the display card or the renderer, infact they waste it. So a 4k*4k image uses ATLEAST 1*4096*4096=17 megs of memory on your graphics card no matter what format you save them in (a pyrtsmidial dss could use far less, but more likely your textyure takes much more space). Further your kindof wasting the entire idea of having that high textures because of the compression artifacts.
Then also remember bigger texture DON'T equate to better quality render, infarct you just go to filtering hell with it most of the time, especially using jpegs. Also you waste e alot of recources for thing in return.
Another note keep textures square and powers of two. As a 3000x4000px uses up as much as 4k*4k most of the time anyway so why not use it. And a ~4000x5000 probably uses 5k*5k- But not only that the square textures draw a bit faster too. For example in the viewport image you have there you prbably never get further down the texture than 2k*2k pyramid. IN factt your noisy quality is probably due to the problematic filtering, that takes 4 times as long as a 2k texture to do btw
