Kali resolution and lags issues

Hello, I recently downloaded the installer file of "kali linux 2021.1" to set up a VM using VirtualBox 6.1.18 r142142. I am trying to run it on a MacBook Pro 16' of late 19 (the one with Intel) running MacOS Big Sur 11.2.3.
Therefore all of the software I'm using are the most recent stable versions up to this moment.

I have set up my VM as usual with the following specs: 8GB ram, 6 cores (100% cap), 128MB Video Memory, VMSVGA Graphic Card (by default), 1 monitor, 50GB of dynamic allocated VDI drive, NAT network settings (by default).
I successfully managed to install Kali on this VM. But there is an issue that I couldn't solve and it's regarding the resolution of the virtual screen of kali. The virtual screen is contained in a very small box, which is ok while I'm installing it, but it becomes very hard to deal with when trying to use kali like this the whole time.

I tried to install the guest additions cd image and run it, but it changed absolutely nothing after the reboot.

When I saw that this still does not work I tried to manually set the resolution of kali from its display settings. But I noticed that the resolution I was looking for, the one of my screen (3072 × 1920) is not available to select.

So since then I let the resolution setting stay on default (2560x1600 - 1x) and I just quitted the idea of using kali in full screen mode, I just use windowed mode adjusting the size of the window in the manner that it looks bigger.
This way it's more acceptable, but as soon as I started using kali I noticed how incredibly slow it is running on my VM.
It looks very laggy and the exact opposite of responsive to my inputs, to the point that while I was on the login page of a generic website (using Firefox CSR) it took 20 seconds from the moment I selected the username input field to the moment that it actually selected, and another 20 seconds from the moment I started typing to the moment when it actually started to show those chars.

I noticed that this I/O lag issue is directly proportional to the size of the VM's window. EG: if I resize the window to be very tiny it looks fairly smooth, as it should be.. but as soon as I resize it bigger it starts lagging.

So I have the main problem: "Kali would not run on my monitor's resolution and I have to manually resize the window to be bigger" that gets me into another problem "when I resize the VM's window the whole thing gets very laggy and unusable".
A solution to either problem is fine for me. I don't necessarily want to use Kali in full screen on my native resolution, I'm fine with the resized window too, but at least I would like it to work properly.

Does anyone know how to solve one of my 2 issues?
I'll be available for further answer to any question you might have on this, that lead to solving the problem.
Thank you.