Lithium Ion batteries like to be cool and they like slow charging.
However, that said, today, batteries can stand a lot more abuse than they used to in the past. Rapid charging and heat tolerance has gone way up so much so that with normal usage, charging with the included 5w charging brick will most likely show no difference vs a 12w iPad brick over the course of two years or more.
The negative about wireless charging in the past is that it does warm up the phone a bit but in my experience with my 8+ it doesn't warm it up enough to harm the battery. Wireless is only 7.5w I believe.
If you're really worried, just use the included 5w brick. That said, I used a 60w Anker charger for the life of my 6+, 6s+ and both after 230 cycles showed within 6% of design capacity.
The heat of wireless charging on my 8+ doesn't worry me at all. Using a 12w iPad brick will heat it up more (and this doesn't bother me either). Leaving it in the sun in a car till the phone shuts down from overheating will affect battery life.
Want to take care of your battery to make it last long? Keep it out of long exposure to the sun, try to keep it above 20%, don't keep it at 100% charge for long periods of time (months), and just use it. Best thing I did for my iPhone happiness was turn off the battery % reader.
I do use coconutBattery on my Mac to record my iPhone's battery health a few times a month (I put into a Google Spreadsheet).
Apple won't even touch your battery unless it is below 80% design capacity. So use it up
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Edit: If you're looking for some extra reading:
http://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
