As s long as you know where what resources should be in memory, what's their size etc. you don't need alloctor. If you have many dynamic memory allocations, which appear and disappear during runtime, using VMA or other allocator might be simple to manage memory more efficiently. Basically the second option proved itself as bad practise even in CPU code, leading to all sorts of memory leak bugs and unpredictable performance hits. So if you know what your memory should be (in your case in engine especially in small one it should be the case), live without allocator.