Hello JonahR
The problem with the buzzy sounds could be you need to increase the buffer size in Sampletank. To do this select the tab called Settings at the top left side of the screen in Sampletank and choose Audio & Midi setup. I have my buffer set at 2048. The performance of your computer has alot to do with this so try increasing whatever you have it set at.
Yes it is possible to use sampletank with BIAB & Real Band however it is not a GM sound module which BIAB uses by default.
In BIAB select MIDI& Audio Driver setup from the Opt. dropdown menu. Select the box that says Use VST/DXI synth also check Route the MIDI through MIDI driver.
In the box below that click in it to pull up the dialog box to select your synth. In the top dropdown box you can select which synth is available and if you do not see sampletank there then select add vsti from that menu and browse to your sampletank location which is usually found in the Steinberg/VSTplugins folder.

Hope this might help you a little.
Brian

BIAB 2025 Ultrapack- Studio One Pro 7 Windows 11, Mac Mini M4 with Logic Pro 11, Melodyne Studio