How to delete contacts from read only accounts
as far as I know, these "read only accounts" relate to other accounts you have set up in Android (e.g. Facebook, WhatsApp, Viber, etc.). These accounts are (usually) synced by default when you set them up and the respective contacts are displayed in your contacts. You have several options to manage these contacts:
1. in Android under contacts go to settings and select "Contacts to display" - here you can chose which account to include in your contacts list. You can also chose a mix of them under "Customize"
2. to manage 'read only' accounts, you may go online to your respective services (e.g. Facebook, WhatsApp, Viber, etc.) and add/modify/delete the contacts there.
3. the best way to manage your Google accounts, at least for me, is still to edit them directly in your contact list at gmail.com. 

Hope this helps a bit.