The festivals are obviously going to be more crowded on weekends,for this festival the concerts are only Friday through Mondays which means that aside from Monday the days with concerts are going to be more crowded than Tuesday through Thursday.In my opinion there's no need to avoid Epcot because the concerts will bring more crowds,the crowds will be there because its a weekend,if you want lower crowd levels then go Monday through Thursday,on Monday you can still catch the concerts and the park won't be as busy.The F&G festival is still like a mini me of the more popular F&W festival where weekends get huge crowds,with that said the word is spreading that even though its a garden festival Epcot has turned it into a smaller version of F&W by adding food and drink booths,so every year the festival will get more crowded just like Food and Wine.
I remember going to Flower and Garden before the recession when the festival was shorter but did have daily concerts just like Food and Wine,basically it was much calmer atmosphere than it is today,obviously people came but even with daily concerts they had no real impact on crowds,a bigger impact is the addition of food and drink booths,I think Epcot has figured that out as you can see pretty much every festival or Holiday has unique food and drink booths.