Apart from some of the more obvious things not to try and take with you on the Strip or Fremont Street for New Years Eve there is other restrictions you might not know about; Among the items not allowed by the Metro Police Department in either place are glass items, backpacks, strollers, coolers or anyone under 18.
The Strip will be closed to traffic after 5 pm today but even before that the Strip is likely to have heavy traffic and as well as crowds slowing down the traffic even more; If you can avoid travelling down the Strip today i would and instead use the parallel streets although it still might not be quick going but still better than the Strip.
RTC local buses will be routed away from the Strip and if you are going to use them i would suggest its earlier in the day and you get to the area you plan to be for the night. If you do wait until a bit later all RTC buses are free from 6 pm tonight until 9 am on New Years Day and additional routes than normal will operate a twenty four hour schedule. The buses will be packed so i would have some patience and if you want a good way from the airport to the Strip or downtown i would check out the Westcliff Airport Express (WAX) which will run every 20 minutes from 6 pm to 4 am.
Yes hotel resorts can block access to their properties because of the crowds, I have been on the Strip on New Years Eve in past years where hotel security blocked access to non guests later in the evening because of the big crowds in the casino. If this happens to you and you really need to get in a certain property i’m not saying you should do this but most likely hotel security might block access from the Strip but might not block access from the other side of the property through the parking garage for example.
Uber and Lyft most likely wont be able to get to their normal pick up and drop off points at the Strip resorts or at least not easily so i would get picked up or dropped off away from the Strip and walk the rest of the way; By walking you might also save some money as both services will be using surge pricing because of the demand.