We are using nopCommerce 3.8 and we would like to automate the payment by credit card process, should we have a button on the nopCommerce admin > Sales > Orders > individual order page, "Charge Credit Card"
When clicked, it should allow the admin to straightaway have the supplied CC charged with the amount set.

will using CC API require OTP to be supplied? if so then it will be a problem.

We are using two CC merchant providers

1. Commonwealth bank (Australia) - we use this for AUD sales
https://www.commbank.com.au/business/merchant-services/bpoint.html?ei=bpoint
We currently have BPOINT Backoffice
Would need to upgrade, and that will need come T&C + policies written
https://www.bpoint.com.au/developers/v3/index.htm#!#gettingstarted
2. Stripe - we use this for all other currencies
3. We do have paypal, but do not use it

I also want an option to enable real time charging that we can turn on later

Implementing Payment plugins (methods) from scratch usually takes 40-80 hours.

nopCommerce has a lot of payments plugins(free and commercial versions).
I think the best option to start with PayPall (nopCommerce team standard package). Please follow the instructions
Configure - PayPal Standard / nopCommerce administration (/Admin/Payment/ConfigureMethod?systemName=Payments.PayPalStandard)
Configure - Credit Card / nopCommerce administration (/Admin/Payment/ConfigureMethod?systemName=Payments.PayPalDirect)
and setup business account.
Additionally, we have source code for nop38:
Payments.BrainTree(nop Team plugin)
PaySera(our plugin. As far as I know it can be good for some EU countries)
Also we used 2Checkout(for customers from EU) and Authorize.net(for customers from US) for some or our customers.

Here is additional list of plugins available for nopCommerce 3.8:
AliPay
Square
CCAvenue
Skrill
Sendinblue
Qualpay
Sermepa
eWay
OkPay
Qualpay
Platron
Uniteller
PayAnyWay
Assist
PayFast

Please, let us know if you would like to add payments plugins(and which one) from not standard nopCommerce package.