Not really familiar with the roads... Pulling a trailer, likely wiser to pick biggest roads possible!

RV’s of all types and sizes travel route 20. The tunnels are rounded but I’ve seen large trucks go through them.

Highway 20 is currently closed. They close it between late November and through December due to avalanches. Updates on road conditions for any Washington state roads can be found on their website. TripAdvisor does not allow links, so type "Washington department of transportation" into the Google search bar. When the site comes up, click on road conditions and any other pertinent links. Many *mountain* roads in Washington may at any time be temporarily closed. It's best to check in advance. If they are closed, they will be blocked, so you won't be able to continue. Sometimes the reason is excessive snow, sometimes ice, sometimes both. Most freeways are always accessible. It is highly advisable to carry tire chains with you if you go on mountain roads in winter. Sometimes it's required, but either way, if the road is icy it is just smart to put them on. Occasionally, there will be people at pullouts for this who will put them on for a small fee. On cleared freeways, you usually don't need them. They can be obtained at most auto parts stores, as well as major big stores, such as Walmart, Target, Home Depot, so on. So, if your vacation plans include skiing, get chains. You will need them. I strongly suggest that since you are not accustomed to icy and snow covered roads, that you stick to the main roads and not travel on less traveled highways. If you slide off the road, you are less likely to be found quickly, and it is not a good idea to try to walk out. Carry kitty litter, candles, matches, warm clothes, energy bars, and water with you if you are anywhere off the beaten path. The kitty litter is used to put under your tires for traction should you get stuck. The candles you light in the car with the windows cracked just a little, to keep the car (barely) above freezing. That way, although you won't be comfortable, you won't freeze to death either should the car not run. Always travel with a full tank of gas when you start out. That way you can run the engine from time to time to keep warm in an emergency situation. I lived in Minnesota in my younger years. These precautions were for all winter! This info isn't intended to scare you. Just to keep you safe. If you get on a snowy road, lightly press the brake at a slow speed to determine the road conditions. If the road is icy, your slow speed will allow you to adjust and stay on the road and you will know what to expect. I hope this helps!

I'm not sure which reviewer might have said there is a Ruby Falls along highway 20. I double checked my reviews of the area, and I did not mention such. But, there is a Ruby Trail and a Ruby Mountain in that area. There is a Ruby Falls in Mount Rainier National Park, but that is not in the North Cascades region. Of course, probably the most famous Ruby Falls, is in Chattanooga, Tennessee, in a cave. We saw it decades ago and it was worth the stop.

Highway 20 is a beautiful drive with fewer vehicles on it. When the higher elevations do get snow, a certain section is closed off over winter. Your time window for your trip should still work. Check the weather forecasts for that time. I do not know who you would contact to get the final confirmation on any road closures.

The national park visitor center in Newhalem is closer to the west end, next to the dam and tourist things associated with it. If the dam and park visitor centers are of utmost importance, then west to east might be better. We went east to west only to avoid traffic on I-5. We live in Vancouver, WA, so it was better for us to drive up from the east and go down I-5 at night when traffic was less. The best scenery from the road is on the eastern end. If you hike, then of course the national park would be the attraction, and that's more on the western end. Since you list Bellevue as your address, you should have plenty of time to take it all in west to east. If you have never been on highway 2, you could also do a loop west to east on 20 and east to west on 2. We drove one time on 2 east to west. Highway 20 is more rugged and has fewer towns/amenities than 2. Hope this helps.