It's like any appliance ... if you have to wear it, you will get used to it and after some practise you can talk and eat without much hassle.  It's only a problem if you let it be one.

I was given a passage, called the Rainbow passage to practise speaking out loud, several times an hour, after I had my expanders bonded.  To begin with there was lisping and spitting and  I felt like I was choking when I ate.  With practise, I was back to talking and eating easily ... within a week.

But it's often written on orthodontic sites that you can talk very easily with Fraenkel appliance because of its thin construction?!

Aber auf KFO-Seiten wird immer geschrieben, dass mit Fränkel-Spangen das Reden sehr einfach wäre, da nicht so klobig?!

I have had a thick bite plate for a few years and I dont often take it out. If I do take it out it is not easy to talk clearly and I stumble over words.
Some time ago I answered the phone without it  and had to go and put it in before I could say much as I could hear that I didnt sound right.
I have an activator as well and it is quite easy to talk with it in now I have got used to it.
I remember seeing a teenager with an activator at the airport but he took it out everytime he wanted to say anything.