It is very difficult to diagnose ticks and rarttles without hearing the noise. Perhaps you could make a short video and post it?
Symptoms you describe would not point me to a lifter. Typically a lifter that leaks down will rattle on cold start up and may or may not settle down when up to operating temp and the symptoms don't exhibit intermittently; they are constant. The other common ailment with lifters is the roller going bad, either the pin holding the roller fails or the hardened surface of the roller flakes off but, again, once this happens, the symptoms don't exhibit intermittently. Of course, the lifters should certainly be inspected.
How to the tensioners look? Have they worn enough to be making contact with the metal holder? I would not rule out and inner cam or outer cam bearing getting ready to fail or even something in the primary. These noises are sometimes very difficult to locate.
I am a strong believer in looking back at the last thing done before an issue starts to exhibit but I don't believe an oil change is the cause of the issue. While I would not pay the Harley tax for the SE 20/50 oil, it is an excellent motor lubricant. I see the oil change related to the rattle as a coincidence but certainly could be missing something.
A compression and leak down test may not reveal anything to help solve the issue but will provide a diagnosis of the condition of the top end. If you plan to change the tensioners, it would be wise to replace the inner cam bearings with a set of full compliment bearings like the Torrington/Timken B148s.
I think it would be wise to address the issue sooner rather than later; could be you are sitting on a time bomb but you won't know until you, or your local guy, takes a closer look. Good luck.