For myself, smoking DMT at the peak of an LSD experience, is certainly different than DMT is, but the ensuing 5 minutes are much more DMT-related than LSD. LSD is not exactly the most comfortable drug for me. When I'm sitting down, I feel like I should be standing up. When I'm standing up, I feel like I should be sitting down. There are often mild back aches or light psychedelic nausea. Sometimes during the LSD, I would smoke DMT as a respite from the LSD. For those next five minutes, it was as if LSD would leave the room. Those aches and discomforts would quickly melt away as I'm plunged into hyperspace.
There's also something the LSD does to extinguish fear or a certain degree of unwarranted intensity that the DMT typically brings, especially pre-flight or during the onset. For some reason, it's just easier to smoke it in that state from a psychological perspective. As for the visions themselves, I would be having these austerely beautiful visions, but there was no psychic toll if that makes any sense. It's like I would get to enjoy these profoundly deep visions, but lacking the overbearing intensity that DMT would typically bring for the same vision accessed without the LSD.
For myself, visions from the synergy would typically invoke certain themes. Celestial visions and feelings would take the primary spot for me. There's also a voodoo magic style at times with this combo. Colors tend to be more intense and saturated, especially compared to the LSD baseline. So surely enough, when those five minutes are up, the extra colors evaporate, and I can feel and see the LSD creeping back in. The aches return, the aesthetic is entirely LSD, and the respite is over.