Dhiten - I am sorry to read of your loss.
To update the register you will need forms DJP and RX3/ST5. Plus a certified or official copy of her death certificate or probate
You don't generally need form ID1 and we don't need the will/deed of variation
Please refer to PG 6 and sections 4 and 8 for guidance -
Devolution on the death of a registered proprietor (PG6) - GOV.UK
You will need to submit the application first and request expedition second
It's only 'quicker' using a solicitor if you are unsure as to what's required re the forms/ST5 or are uncertain in any way. A solicitor/conveyancer will be familiar with the process, forms and more