I feel you on the sweet tobaccos, they're grim.
As others have mentioned, more PG, more nic and higher coil (rebuildables only) are the main factors in throat hit. As you're not rebuilding that just leaves more PG and more nic. 50/50 is a reasonable level of PG, I don't think you would benefit from going much higher. You probably wouldn't want to go much higher with nicotine, and commercially available liquids peak at 20mg in the UK (because of the bloody TPD).
I've never tried the tigon, but I find the sceptre 2 (innokin) gives a decent level of hit for a simple device. It's only 17 quid or so, so it might be worth a go. I think the coils are 0.6 or thereabouts. So for the tigon too, you could try using one of the lower ohm coil options to see if that helps. It might. Normally lower ohm coils are suited to lower nic level eliquids, but you *might* find with your current liquid that it hits the spot for you.
Edit to add: Might be worth exercising a little bit of caution chain vaping if you're using a lower ohm coil with an 18mg eliquid. I've done it before and overnicotining is not nice