We really like Spelling Power. We aren’t using it as much this year, but I plan to add it back after Christmas. I just needed to give myself a break from something that was parent-intensive. I will say SP is not very independent, but if you tweaked it I suppose it could be moreso.
We do use ILL and PLL. My 10YO son, 5th grade, is using ILL (he never used PLL b/c we were using Daily Grams at the time he would have used PLL; live and learn; that didn’t work for us at all).
My 12YO son, 6th grade but only speaking English since 2010, uses PLL. I expect him to finish with PLL this year. I don’t expect 10YO DS to finish ILL until next year sometime.
Here’s is what I did with it: we use it almost exclusively orally. I have found even with my ELL student that he does better with copywork from a book rather than the written work in PLL. So I just go over each lesson with them orally. We often skip the picture studies, because we do those in other ways. If a lesson seems like something they already know, I skip it. If a lesson seems to leave them confused, I make a note to myself to go back over it at a later date just to see if they really got it.
I do think over time it really works. For what its worth, I consider PLL to be HUGELY helpful to my 12YO son, who is still what I consider an ELL student. I credit it the most with how far he has come in his grasp and comprehension of the language (so that says a great deal for me in favor of PLL).
But as with every resource, mileage varies. I would say if it isn’t working, try something else. I am happy with it, but I won’t say the boys love it. None of mine though love grammar/language instruction except DD, who is 7.
HTH