Bidding Strong Hands
The most usual way of bidding very strong hands is to use an opening 2C to indicate 23 or more points, regardless of distribution. It suggests nothing about the club suit. A response of 2D is negative and reponder is forced to bid even with zero points.
An opening 2NT shows 20-22 points with a balanced hand. This would preclude the use of 2NT for the 'Unusual No Trump' convention.
Opening 2D, 2H or 2S indicates a preference for that suit as trumps with either 8 playing tricks OR 20 - 22 points and an unbalanced hand.
As many players now use an opening 2 of a major as a weak opening with 6+ cards in that suit and less than opening points, there is a conflict on now being unable to bid a strong 2 major as an opening bid.
One way to overcome the weak 2 major and unusual 2NT issues is to bid as follows
2C 23+ points (2D negative response)
2D 20-22 points or 8 playing tricks in NT or any suit (2NT is a negative response and unless opener is OK to play on 2NT, should be 'taken out' into opener's preferred suit.)
2H or 2S - a weak (pre-emptive) bid with at least 6 cards in the suit and less than opening points but probably at least 8 points depending on length and distribution.
2NT - 2NT Minor Suit convention showing both minors with at least 5 cards in each minor.