I find using a partition other than the boot drive, and setting the minimum swap file size to 2.5 times the available RAM, gives a bit of speed bonus. Example: 40GB (37 actual GB) drive on PC with 240MB RAM (256MB RAM minus 16MB for embedded video device)...
32GB Win9x boot partition, labelled Win98sys
5GB data partition, labelled SWAP
In Performance I select 'Manage swap file manually'
Drive: select D: (second partition)
Minimum size 600MB
Maximum size either auto (set to max free on D:) or 960MB (4 times available RAM). This moves the swap file off the boot partition (making it less painful to scandisk and defrag), and subjects it to less chance of fragmentation. The permanent swap file (minimum size) handles most tasks without the need for creating or resizing the file, while the temporary space allowance lets you stash forseeable back tasks.
Mounting over 512MB RAM (after video and sound devices have hogged their share, if embedded) in a Win98 or 98SE machine is not recommended, the OS stumbles on it. XP is set up to handle gigs of RAM if you need that much. If you have that much RAM you probably don't need a swap file.