I have a United States Iphone SE. Will this work in Switzerland? I will have to book advance business from the states before I go over and give out the number I will be using in Switzerland. Is it easier to get some sort of international plan? or is it easy to buy a burner phone ahead of time from the US and already have the number? Do they have burner smartphones?
You'll need to call your mobile operator or search their website to find out if they provide reasonable roaming fees for Europe. E.g. tmobile have plans that provide free international roaming in most countries.
Unless your iphone is unlocked you won't be able to insert another sim card, so a cheap unlocked phone with a sim card you buy on arrival at the airport might be the easiest option.
The iPhone SE is a multi-band phone meaning it supports both CDMA and GSM, as well as LTE for data.
Because of the GSM support, it will work in Switzerland and all of Europe for voice calls.
However, be sure your rate plan allows International Roaming and you are aware of what costs this might bring. You may also need a GSM SIM card to enable usage in Europe, particularly if you use Verizon or Sprint.
You best course of action is to visit one of you carrier's stores to get setup and acquire SIM if you need it, especially if you need to keep your domestic number.
If you're are willing to use a temporary number while in Europe, you can buy a local SIM when you get there.