You might wanna try out Pilot Vpen [1] - its a disposable fountain pen available in a couple of colour options. I've been using them for 3 years now without issues, and no blobs form (generally, unless the paper was a tissue paper or smth)
Are the 78Gs still manufactured, or have they been replaced with the Metropolitan? I haven't directly compared the 78G with Metropolitan, but I've been disappointed with how wide my Metro writes despite having a fine nib.
[1] https://www.jetpens.com/Pilot-Vpen-Disposable-Fountain-Pen-B...