I’ve recently used https://miro.com/ and overall was a good experience to collaborate
In addition to the software, make sure your team has good hardware. A screen large enough with high enough resolution is critical to see the whiteboard. What’s also important is that video from meetings takes up screen real estate and with multiple participants, having enough size and resolution to see them all helps you stay connected. External webcams that can be adjusted are helpful also.
I want to achieve the same productivity, but I'm very concerned about fatigue. I'm thinking we'll need to break our ideation sessions down into a greater number of shorter sessions.
Virtual meeting fatigue is real because there aren’t as many natural breaks. It is important to make sure that people know they can excuse themselves for water/food/bio breaks.
I’ve also found that virtual whiteboarding is slower for me as I’m used to picking up a dry erase marker. It takes time to adjust to the different work stream but a huge benefit is the quality of the end product (no sloppy hand writing, easy to modify).
I don’t have any direct advice geared towards your situation as our white boarding and planning phases are quite different in my industry.
I think being clear with the team up front about these trade-offs will make the transition to remote ideation smoother as people will hopefully be less frustrated that ideas aren't flowing 'like they used to', but perhaps they can flow better and in new, more productive ways. We shall see.
Sincerely, thank you!