Some distributors call LDF other things like “lightweight MDF”. It isn’t super critical especially if you go with 1/2" thick MDF instead of 3/4" as the top plate.
I have generally avoided that style because they lose a bunch more suction if you uncover a hole while cutting vs a plain MDF top. Typically you have to put another thin layer of permeable material (such as Datron’s vac card or this: Black Box Grip-Lock Mat - Black Box Vacuum) on top in order to prevent loss of vacuum. You also must cover any unused area every time. I know that style can work and have used it in the past, it just takes more thought and planning to use. The industry standard on large machines is to use a plain MDF/LDF top because of the ease of use and lower CFM requirements to get the same level of vacuum. I’ll never go back now that I do it this way. You can see my Avid based machine with the table I made here: Chasing zeros on a Shapeoko 3 - #26 by nwallace
The picture shows the table before I put the 5x10 piece of LDF down.
A large shop vac should work fine. One thing to keep in mind is that most shop vacs are cooled by the air they suck in. In a case like this there won’t be much air moving through which could shorten the life of the motor if it gets too warm. Just keep an eye on it and try not to run it for hours at a time.