Whether load sharing is possible depends a bit on what your topology is, and on how the VPNs are configured. In configuring the site to site VPN are you specifying a source address for the VPN packets, and if so what is it? What are you specifying as the peer address for the VPN and what does your routing table have for how to get to those addresses? If you have multiple paths to the VPN peer address (and if they have multiple paths back to you) then load sharing may be possible.
One of the assumptions in cef load sharing is that there would be multiple destinations and that traffic would generally be distributed accross those destinations. When you run a VPN it does make it look like a lot of traffic is going to a single destination and this would tend to bias the load sharing and put greater load on one of the links.
We are pleased to announce availability of Beta software for 16.6.3. 16.6.3 will be the second rebuild on the 16.6 release train targeted towards Catalyst 9500/9400/9300/3850/3650 switching platforms. We are looking for early feedback from custome...