Let me share my experience in applying Surrender + Visa.
1. I took appointment in Brampton BLS office and chose 'Visa' as reason and gave my passport number (I did this even before my oath, estimating the time it would take me to get Canadian passport in hand)
2. I made sure to have Canadian citizenship certificate + passport before appt day.
3. For surrender docs, follow instructions at:
https://www.blsindia-canada.com/toronto-jurisdiction/surrender-of-india-citizenship.php
It consists of filling an online form and taking printout of it (having a printer at home is invaluable) and making copies of all documents asked. I also signed my document copies.
4. For visa, I chose 'Entry visa' as this is the most appropriate category for OCI's and currently we get it for 6 months, Tourist visa only for 1 month. Instructions here:
https://www.blsindia-canada.com/toronto-jurisdiction/entry-visa.php
5. I took printout of the surrender and visa forms, checklists and supporting documents to BLS. I didnt take any photos as I knew BLS provides that service on the spot.
6. Went to BLS at my appointment time, they checked my name on list of appts and gave me ticket number, which didnt take long to be called.
7. At the counter, they took my Surrender form and copies of docs first and my Indian passport. Then my visa forms + Canadian passport. I forgot to take a photocopy of one of my docs, so they took it for me. They also asked me to have my photos taken and come back to the counter with them. They needed 2 photos (1 for surrender and 1 for visa), I took 2 more for future OCI process on their advice. Cost was $30 for 4 photos.
7. They confirmed where I want my docs mailed. I didn't want to drive all the way to Brampton, so I agreed to them sending everything back by courier. All taken together (photos, fees, courier) the cost came to ~$350.
The process was pretty smooth and staff were courteous. They were letting people pull things up on their phones if they forgot any document. They make small corrections on the
visa form (dont know about surrender) themselves if needed and that seems to be ok.
They didn't ask to see any originals, but I carried them anyway. The only originals I had to give them were my Indian passport (for surrender) and Canadian passport (for visa). They said visa takes up to 12 business days to process. They also said my Indian passport will be cancelled and returned back to me (I like that, since I want to keep it as a souvenir).
They gave me a bunch of receipts with tracking numbers to track application. I also received a text message and email with stating that my docs have been accepted by BLS.
I asked about OCI process and they confirmed that it can only be done after Surrender is received (4-6 weeks). They said I can do walk in for OCI on a Saturday (even though notice stuck outside the place says otherwise). I will try to take an appointment just in case anyway. I have read from previous posters that if no OCI appt is available, one can use 'Visa' category and do OCI anyway.