HI plhbn and welcome you have come to the right place.
Ive had a decent amount of experience with oral forms of sumatriptan all forms actually apart from the injections as they are $160 i my country.
Before I was first diagnosed with Clusters, I and the doctors thought I was having migraines and I was prescribed Sumatriptan tablets. In the early days of my headaches they were much less frequent. The tablets definitely worked better than otc and opioid painkillers I had tried and actually would kill the headache. The problem being they did take a long time to kick in, minimum 30 mins to an hour. That feels like a long when you are in agony.
After being diagnosed with clusters I was prescribed the nasal spray version. I found that to be very hit and miss. My nose gets totally blocked sometimes so I felt it didnt even get into my system. At times it worked and It would start to kill the headache in about 20 to 40 minutes.
I then tryed the wafer version, you put that in you mouth and it dissolves, I found that to work pretty well usually working in 20 to 40 minutes.
The key I found with all oral Triptans is that If you take them as soon as you feel you might have a headache coming on the more success you have at aborting the Headache quickly. Also Drinking strong coffee or a energy drink seems to make it more effective also. This method was effective for me for a fair while.
The problem I found was The worse my condition got the more I needed to take them. Not only did they start losing effectiveness but I started to feel very average, tight felling in the chest, high blood pressure, even more tired than usual, a walking zombie pretty much. At times a Headache would hit so fast and was so strong that I would take one and it wouldn't work so after an hour of agony I would take another one out of desperation then that still didnt work for another 40 minutes. Then I felt so crap for the rest of the day dizzy tired, and a few hours later it would happen again. Maybe because of a rebound effect or maybe not im not sure.
Once I moved to Oxygen I felt much better.
In closing oral Triptans were a saviour for me for a fair while when used at first signs of headache with caffeine and taken sparingly but were not the long term solution.
Tread carefully and goodluck, There is a lot of information on this forum to help you improve you pain. Plenty of people to provide answers to your questions.
Dan