10-4 on the particle board BUT, again, what are the nails/staples going to 'grab' onto??? If you use particle board, I guarantee you that the 3/4" board WILL in short order not hold the flooring down. Besides, if you read the Warranty AND the Intallation Instructions, I will bet dime to dollar that you will VOID the Warranty if you use particle board. Again, BEFORE you buy or install ANYTHING, be sure you read the enclosed paperwork first.
Now, as far as a recommendation, 3/4" varies from mfgr. to mfgr. You will find Bruce in Home Depot. It's very good quality. As for its price, it depends on the wood, the finish, AND where you live.
RE: Engineered Flooring, there are ALL kinds of floors. The price difference will be in the number of cross-layers AND the type of wood in the cross layers. Also, the THICKNESS of the top-most layer will affect the price. Some engineered floors are OK to refinish. Some aren't. AND, this depends on if it's glued or stapled too. You need to ask these questions IN ADVANCE and even confirm it w/the mfgr. Most all of the Mfgrs. have WEB sites that you can e-mail them. Just be CLEAR w/your ?'s and keep a copy of their reply.
I wish I could offer more but you need to do some shopping and ask questions. Believe me, you'll be WELL educated by the time you're through!
My best to ya and hope this helps.
Jay J -Moderator.
PS: Again, BEFORE you buy, if you're thinking of doing the Installation yourself, get a copy (Xerox if necessary) of the instructions to see if you can rent the necessary equipment that's specified in the paperwork. (THey're pretty good about that.) And, be aware that if you do this job on the weekend, is the Rental Agency open if you have a 'problem' or question? (This type of DIY work isn't easy AND you need to know a little more than what just the instructions say. BUT, if you're confident enough, ya know ...)