Whatever the writing, head has to lead the way. Depending on the slant in fiction 'heart' has its place, although style also depends on presentation and that's 'heads up' as well. Poetry probably also relies on 'head' to some extent (metre etc), although the content is down to the individual as long as it's not soppily presented. No-one likes to read 'soppy' stuff, even poetry. I don't dabble in poetry.
Straight prose - with a twist of humour maybe - is more up my street. Everybody needs to be lightened up a bit whilst they're being enlightened. You can overdose on 'Gothic' poetry. Being immersed in the 'dark humours', Keats, Shelley & Co. all tended to dabble in the laudanum doses. I suppose it helped them attune themselves and it sold well in Victorian England - or pre-20th Century polite US/Canadian society.
Your 'soul' shows in your writing style through your choice of words and how you place them. Your head tells you your writing is worth reading.
As for 'synergistic', see above (Keats, Shelley) and see where that gets you: short cut to the padded cell and long-sleeved jerkin. Where's the fun in that? Besides, you wouldn't appreciate your Hub-Pages PayPal payouts, would you... (rhetorical question).