Your canon material for study: 'That Naughty Flashback Scene'
Ready, steady, GO!
Except I don't read that sequences as "boiling down" to that. It lands there as part of a continuing arc that begins with hurt, and lands at planning only as an assessment of why Lu would be better matched with Bill. Bill only comes up in *Klaus'* argument as a direct response to Lu's answer...and rather than staying with the topic, when she wants to know how he's going to stop her his answer is to provide her with one of the better kisses in the comic. A kiss he honestly thinks is enough to talk a stubborn, independent, kick-ass woman out of marrying one man who adores her, and staying with Klaus.
That in and of itself indicates that there was more in that kiss than just "good times, great orgasms." The only real trump to "He loves me, and is going to marry me," is pretty much, "I love you more -- and you love me more." To me it looks like that's what Klaus offers, with the whole "plan/Bill" thing being only a fraction of a larger discussion. (wry grin) Klaus seemed quite sure is was a completely convincing argument...and even Lu found it compelling. Just...just that if it was compelling, there was all the more reason for the drugged wine.