Q.Blackberries and raspberries
I did not cut back the bushes when I planted them. They appeared to have been cut back when potted for sale. Had grown some and had some frost damage.
Will this stunt them in future?
I tilled the ground, adding some fertilizer, planted, then spread newspaper, then mulch.
(I’m attempting to choke out the bindweed)
Will the paper and mulch ruin the soil for the berries?
I recommend only fertilizing once a year for these, as they will sustain without much feed. Now, as far as cutting them back... These two are related, closely, and will have similar growth habits. They fruit on older canes. This means that you will want to leave a good section of the older, thicker wood for it to fruit properly.
As far as what you have done to the soil... this can be a bit of a challenge, as this can also encourage rot. I would suggest using dolomite lime, and putting some wettable sulfur in the soil to prevent any rot from occurring. One method to controlling weeds is to mix vinegar in water 1:1. Half vinegar and half water. Spray ONLY the plants that you intend to kill and try to avoid spraying the soil if possible. Here is an article that will help further: https://www.gardeningknowhow.com/edible/fruits/blackberries/growing-blackberry-bushes.htm