Presumably you are about to go on your first RS tour?
The guide and driver do not accept tips, and in 13 tours there has only been 1 tour where some of the people went together to buy a little something. It's not really done.

Palinka or Unicum

The way I look at it is that this is a professional business relationship, not an invitation to a personal friendship. They could be interacting with hundreds of people in a season.

One group got together and bought a gag gift for the guide, but really they are not supposed to take tips or gifts. They don't necessarily get to go home after each tour either, so carrying around a bunch of gifts would be a burden.

See this lengthy related discussion about tipping which includes much discussion about gifts. TL:DR version: a handwritten thank you note and good review is sufficient, especially for a guide that may not have room to pack extra stuff as they move on to their next tour.
https://community.ricksteves.com/travel-forum/tours/tipping-rs-guide

OTOH, who doesn't like chocolate (or booze, as Mr. E suggests)?

On my 21 Day Best of Europe tour I gave all my leftover Swiss Francs to the bus driver who was going a couple more tours after mine.

I usually take greeting cards with landscape photos from my home area so I can write thank you notes to the guide and driver.

Rarely I've had tour members come up with a gag gift...on the Best of England tour more than half the members were retired teachers. The joke was the frequent singing of "The wheels of the bus go round and round". One of the tour members found the book in a shop along the way so we all signed it and presented it. Quite funny. That tour ends in London where the guide lived so we figured he could drop it off easily.

With the small group tours I'm taking now, I know the guide well and know he loves good chocolate. Last tour I stopped at an artisanal chocolatier the day the tour started and gave him some at the beginning of the tour. That is not really something you could do if you don't know the guide, though.

Otherwise, I would not bring gifts for the guide and driver. I do agree it's a professional relationship and they are on the road for several months often without returning home.

Imagine 28 people giving gifts; then they are on to the next tour and 28 more people giving gifts. We've been on 3 RS tours and there is no gift giving. They are also in the midst of traveling; not necessarily home for quite some time. They have no more room for extras than you do in your carry on. A simple thank you and a nice email to the RS headquarters regarding the wonderful service received by specific people seems thank you enough.

Our RS guides always address no tipping including to them during orientation.

As a former tour director, let me point out a couple of things mentioned in this thread:

They don't necessarily get to go home after each tour either, so carrying around a bunch of gifts would be a burden.

And

they are on the road for several months often without returning home.

While the thought it nice, anything extra can be a real burden. I hate to admit it but many gifts get left with the hotel staff. Even booze and chocolate. (Think about it, your RS guide probably has carry on luggage. You give him a bottle of booze. He has to fly the next day to a new city to start a tour. What does he do? Check his bag so he can take the booze? No. It get "regifted" to someone at the hotel.)

If you really like your "guide," one of the best things you can do is leave him/her a great review.

Oh, I thought of something else. I do try to buy the guide and driver drinks along the way. Not as part of the group but ask if they'd like to meet before dinner in the hotel bar (if there is one) or a nearby location. This generally seems to be appreciated.

He has to fly the next day to a new city to start a tour. What does he
do?

Party!

Thank you all for your very helpful comments!