A combination of disabling Hardware Acceleration in other running applications as you suggest Leafbeard and a slight tweak to Kinsington’s solution regarding the “Max Background FPS” option earlier in this thread (Game is freezing when I alt tab - #3 by Kinsington-stormrage) - I left it enabled and set it to exactly match my chosen value for the Graphics option immediately above it (Max Foreground FPS if memory serves) - has solved this issue for me.
Thank you both for the guidance. Much appreciated. The alt-tab freezing was driving me absolutely bonkers.
Edited addition: For anyone comfortable with making Registry changes, here is a link with another fix for this that has resolved the issue for others. While I personally went with the method described above in this post, this might be a good alternative if you can’t disable Hardware Acceleration in other running applications. Game freezes when alt+tabbing (new 11.1) - #8 by Battlecruisr-kiljaeden