Buy a decent set of appliances. Some are better at keeping the spin cycle balanced.

Otherwise, not really sure there is much that can be done outside of good building practices.

@David Cary - we have already purchased the..

LG 7.4 cu. ft. Ultra Large Capacity Smart wi-fi Enabled Front Load Electric Dryer with TurboSteam™ and Built-In Intelligence

and

LG 5.0 cu. ft. Mega Capacity Smart wi-fi Enabled Front Load Washer with TurboWash™ 360° and Built-In Intelligence set (hopefully you approve)

As you know with Covid, appliances are taking 6+ months to get in stock (I have a friend who ordered her refrigerator July of last year and is still waiting) these only had a wait-time of 3 months (our Thermador appliances were ordered in December and, fingers crossed, will be here at the end of June)

Given the above, I assume additional bracing is the best way to go ?

@chispa thank you - I expect some vibration and noise so not too worried but I just would prefer not to feel like I am actually "in" the spin cycle (LOL) so figured anything additional we could do during the build to help is better than nothing

In my experience, overengineering your floor joists for the 2nd floor (i.e. did you have an architect / engineer spec this out?) and you will do a better job at isolating the movement than 90% of the homes that I see that "meet code".

You could try anti-vibration or vibration isolation pads under the feet of the appliances.

We are building and have laundry room opposite the family room wall, with a built-in bookcase in between. We have put sound proofing in the walls, which may or may not help. Last week, I read a similar W/D vibration thread. Someone suggested a trick that they had success with. They put pool noodles underneath the side edges of their washing machine and the vibration stopped. When I was in Lowe's the other day, I spied some narrow star shaped (for the 4th of July) noodles in white. I snagged one to use just in case we have a vibration problem. Cut in half, they are the perfect length for under the edges of my washing machine.

It just will not work out without vibration/shaking issues in a newer home 2nd floor. If you have a basement put any front load washer down there. Unseen structural damage can happen over time as a result of vibration and shaking from a front load washer. I was a builder for many years and this issue resulted in some enclosed garage laundry areas when feasible or plumbed later and moved to basement. Good luck.

Back in the day I put my washer on a ~1/4 inch steel plate which itself was on 4 anti-vibration pads (some sort of foam/rubber with dimples). It seemed to do the trick.