The thing with win9x on dosbox pure is that it makes a hard drive image running the os. Then you have to mount the image of the game to install it. This means you probably have to make a different image with the os and the game installed auto running during startup for every seperate game.
I don't think there's an easy and disk space efficient way to do this unfortunately.
As for installing windows 98, you have to create a hard disk image with imgmake first. Then you have to mount the boot disk as floppy, and the windows cd as cd rom drive. Only then can you install windows 98. You don't need a boot floppy only if you have the OEM Full edition.