Does devotion differ when done in a group versus when done alone?
Whatever way of devotion is convenient and possible for you is fine. However, when there are devotees doing meditation together, they all have their own vibration of devotion in the atmosphere and sometime this can help to uplift another devotee. So both ways are equally good, either doing alone or doing in group.
What is surrender?
We must be like a day-old child..., and surrender our mind to God and Guru.