You should not really have an issue with a Draytek to ASA VPN, we have many of those running on multiple ASA firmwares and 2820s, 2860s (v3.9.4.1), 2862s, 29xx etc.
I can't specifically tell you how, as I am not the Cisco guy :-) If it helps most of ours run on IKEv1 with 3DES with auth, no PFS. We also run all the tunnels outbound on the Draytek to the Cisco., with P1 28800 and P2 3600, which is the Draytek default.
The solution is reasonably well documented on the Draytek knowledge bases and forums, and your Draytek reseller should have access to Draytek tech support, who are pretty helpful most of the time if you are clear on what the problem is.
Not wishing to undermine stephenw10 on the pfSense sell ;-), we have had no luck really in getting Draytek to play with pfSense running in Azure. Despite our best efforts we cannot get a stable solution. We can get pfSense to work with ASA all day long though, so it depends which end you might switch out for a pfSense.
