I have the same exact issue on ArcoLinux (as host system) with Windows 10 as VM guest and have installed spice-guest-tool-0.141.exe (2018 version), as it was the most recent available file I have found. The spice-guest-tool installation solved the problem of being finally able to obtain the copy-paste functionality between host and guest OSs, but caused the resolution issue...
This might be of some interest: https://www.reddit.com/r/VFIO/comments/aqk2pk/qemukvm_4k_resolutions_using_qxl_via_command_line/
I ran into something that I couldn't find an easier answer for and figured I'd post it here rather than find a specific distro wiki so I could give back something(tm) to everyone. ;) If anyone found a location explaining this topic more linearly feel free to refer to it for me so I learn to search better.
I run a 3440x1440 monitor and run Gentoo with Windows VM's where I needed larger than the 2560x1600 max resolution of the standard QXL video driver. I googled (copyright curtailing verb form not proper noun...) multiple ways to do this for Ubuntu and libvirt XML but nothing for the command line. As I was about to post the question to reddit I found this:
I can confirm Andrei Stepanov's command line works after I switch from
qxl (which is also what's in the spice tools package) to the qxldod
drivers in the the virtio 0.1.141 iso. I did have to switch to the
drivers first then apply the video ram settings between reboot but
that may be anectodal or transient to my scenerio using Windows 10. I
believe guest support for Linux is far more straight forward with the
same QEMU parameters. You may have to expand for larger resolutions.
The math for it is elsewhere in the mainstream articles/posts.
-vga qxl -global qxl-vga.ram_size=134217728 -global qxl-vga.vram_size=134217728 -global qxl-vga.vgamem_mb=32
I had never known about the "-global" method of passing other
parameters to QEMU. Something for me to learn about in the future
more. Otherwise, there is enough on the internetz already to act on a
libvirt solution.. I just haven't converted over, yet. Reading up on
pvpanic does lend me to move towards something more advanced when I
have time, though.