You can utilize two URL customizations to control the payment types for applicable membership levels.
Scheduled Payments option is uneditable
By adding &paymenttype=scheduledonly to the end of the membership form URL, you can open the scheduled payment option when selecting a membership level. Purchasers won't be able to deselect the scheduled payment option. Purchasers can set up the recurring payment schedule that works for them.
Scheduled Payments option is editable
The scheduled payment option gets opened when an applicable membership level is selected by adding &paymenttype=scheduled to the end of the membership URL. Purchasers can deselect the scheduled payment option. Purchasers can set up the recurring payment schedule that works for them.
Additional Information on URL Customizations: