I’ve got the DeWalt plunge base for their trim router and it works well enough. You don’t need it, unless your design doesn’t have a wide enough area to tilt the router into place.
As for the inlay kit, I say buy-once-cry-once. You might find you use it more than you think!
Ryan/// ~sigh~ I blew up another bowl. Moke told me "I made the inside bigger than the outside".