Until I joined WW, I didn't even know these were a thing, and believe me, I've attended my fair share of OOT weddings. I know wedding party gifts are standard, as are some type of favor (preferably edible), but it literally never crossed my mind to purchase gifts for our OOT guest staying under our room block. I would venture to say that for about 70% of our guests (we are inviting 200+, anticipating around 150), this will be considered a "destination wedding" to them (2+ hrs of travel time). With that being said, we are 4 months out from our wedding, and while some have reserved their rooms, many have not, and won't until our invites are sent out. Our blocks also allow guests to reserve for 1-2 nights (Friday before, Saturday after or both), so we also have no idea when and for how long guests will be coming down/staying.
I should also mention that due to the number of OOT guests we are anticipating, only our immediate families, wedding parties and their families are invited to our RD (roughly 50 total). So I guess my questions are: is it 100% necessary to do a "welcome" gift, and if so, what do we include? Also, should we wait until after our RSVP deadline to purchase them if that's the case?