Is it actually any good for speaking abilities to speak aloud while reading?

Only if you know the correct pronunciation and intonation can you self correct. Otherwise you'll probably be repeating the same pronunciation mistakes. With that being said, you can definitely practice connected speech by speaking aloud. (I'm a learner of English. Anyone is welcome to correct me or rephrase my words for me, making it more sound more natural. Really appreciate it.)

For pronunciation, I can see how that would be beneficial. For actual conversation abilities, where you need to not only form sentences but do them *quickly* and *accurately*, it might not actually be that helpful. But if you struggle with pronunciation or want to improve your accent, reading aloud should definitely help!

i helped me, when i was workign towards the next level in french. reading aloud is about more than pronunciation. you need to scan ahead of the word you're saying to see how the sentence is going to develop and end. this helps you to plan pacing and inflection and things like that. idk if it improved my pronunciation in french. i tend to believe most people reach a level where they have the accent they have, and so long as it's understandable it's unlikely to change beyond that. but reading aloud in french absolutely made me a more fluent speaker. eta: the other - and really important imo - thing it did was take me beyond my comfort level. once you get to a certain point with a language, it's hard to get past it because you already know less sophisticated ways of saying most things. with a book, i didn't choose the words so i had to adapt and grow. emile zola had never heard of me; he didn't write his books to be read out loud by an anglo student.