You should be perfectly safe with the subox mini at up to 50 watts, atty resistance makes no difference to battery amp draw in a variable wattage mod. This is all about the watts.
If your actual battery is heating up, it may be the wrong type of Li-ion battery. You should be using one that is rated for at least 20 amps continuous. Mooch did a whole lot of battery testing and put together a list of most of our typical batts. The list is in a PDF file that he has attached at the end of
the blog entry here. Batts like the Samsung 25R, LG HE2, Sony VTC4 and VTC5 are all great choices. The higher the mAh, the longer you will be able to vape on a charge. I only buy vape batteries from known good suppliers that will not sell me counterfeit batts, like Illumination Supply, RTD Vapor and imrbatteries.com.
If the heat is coming from the RDA and is warming up the mod you're fine.
Yes, the higher you set the watts, the less vape time you'll get per charge. Twice the watts = just about half the vape time.
The subox mini is a great mod. If you want to upgrade, it all depends what you want in the next mod. More power is pretty straightforward and you can also get dual 18650 mods which will run twice as long per charge at the same power. It's really up to you and what you want.
