Go back to cigarettes? That infuriates me. Just so you know, health authorities in many countries are recommending vaping for harm reduction. There's good evidence that it's much safER than cigarettes. As for the 'issues' with e-cigs, all the evidence there is that the problems are related to an unsafe cutting agent used for vaping something other than nicotine. Avoid the black market and 'other' substances, and enjoy being cigarette-free.
OK, on to the ejuice. Whether it's for the Juul or another device, the bulk of ejuice is made of a mix of VG and PG. It's possible to be sensitive to either of those. VG sensitivity tends to manifest as wheeziness or a heavy feeling in the chest, so there's a fair chance that it's your culprit. Additionally, Juul uses a relatively low proportion of VG (30%), while a lot of other ejuices have more (70% - 90%). If your new juice is higher in PG, that would explain why you were OK with the Juul but had problems with the Boulder.
So, it looks like you need a low-VG, high-PG juice. They're harder to find than juices with higher VG, but they do exist. If you wouldn't mind telling us what country you're from, someone around here will be able to direct you to a supplier in your vicinity.
'Hit' is mostly from nicotine level, so it might be worth thinking about increasing that. The 'throat hit' part of the hit is the main difference between freebase nic and salt nic; salt nic was developed to have a lower throat hit so juices could use a higher concentration of nicotine without choking the vaper. Under the circumstances, you might actually prefer freebase nic to salt nic, but it's probably worth experimenting a little. By the way, what ejuice are you using now with the Boulder?
That's about all I have to suggest at the moment - low VG juice with whichever type of nic you think you'd prefer. I make most of my own juice so I'm not a good source for a specific recommendation, but I expect someone will be along soon who can be more helpful there.