Swiss meringue vs Italian meringue and can I use one of these ....

smbc and imbc taste alike. smbc is easier to make. You will see people making it on youtube. I have made imbc lots of time and love it, but now i make smbc , because it is easier to make. People that make both do use it under fondant. They chill it first, before putting the fondant on and they keep it chilled after the fondant until they get ready to deliver. Recipes for both are on this site. On youtube you can search for Dyannbakes making swiss meringue buttercream. It is very easy to make. hth

There is also a free class on craftsy.com for making a SMBC that is good.  I like the recipe but I do use salted European butter because I like the taste better but that is just my preference.  Have fun with it.
 

I use SMBC all the time, mainly because of the flavour.  It's very buttery, so if you (or your clients) prefer the taste of butter to the taste of regular BC, then definitely try it.

This is the method and recipe I use...it's quite easy...a little more labour-intensive than regular BC, but worth it, IMO.

http://sweetapolita.com/2011/04/swiss-meringue-buttercream-demystified/

I use salted butter, and don't add the salt suggested in the recipe, but that's just my choice.  And...I use the egg whites that come in a carton...easier than separating eggs, which for me means putting them on opposite sides of the room.  I can't separate an egg to save my life.  :-)

Keep in mind it doesn't crust, but goes hard (like butter) when you put it in the fridge.  I found that smoothing it using the usual methods (hot spatula, for example) doesn't work nicely on icing I've coloured, as it smears the oils in the butter, leaving colour spotches.  I'm considering going back to crusting buttercream for any coloured cake I need a smooth top on.  However, I love the flavour of SMBC.  So it'll be my mainstay.  :-)

I have started subbing in one stick of salted butter in my buttercreams, I feel like it just makes that little difference. And I make Rose Levy's neo-classic buttercream with the yolks!