Many old masters used camera obscuras which is only the equivalent of projectors etc or using the computer.
I don't like grids or tracing - so for me it doesn't work. It makes my work go stiff and and I hate it - I need the slight inconsistencies, the natural distortions that I add unconsciously, that emphasise lines and compositions.
I like my lines to be fluid and rapidly drawn and none of that is possible with tracing - for me anyway. If you draw a fluid flowing line fast and then copy it slowly, tracing or gridding, it loses the spontaneity of the original. To me that's important but it isn't in everyone's work - so it depends on the work you do whether it's better to work freehand or not.
I'm totally right brained on tests (with zero organisational skills! ) and I think those with a higher left brain element may gain from grids/tracing, unlike me.
I do think freehand sketching is important though and that not all work is done by tracing/gridding and that work is done from life not always photos if you are to develop your skills.
I use the computer regularly to work through ideas, scanning in sketches and changing them.
This is a doodle I did while the class were all occupied, no-one needed help and the coloured pencils were sitting in front of me ....
and then I played with it in Photoshop, creating a repeat pattern
and then altering the colours.
I did some more work to the trees&rocks painting today, using oil paint but it's wet and so won't photograph without shine. I'll post on the progress in a couple of days probably.