I don't think few dozens howitzers and MLRS gonna change incredible quantity advantage Russians have, not to mention they gonna target those weapons with air and missile strikes as priority targets, as they already doing, yesterday video posted on twitter of destruction of Norwegian donated howitzers.
This whole talk about wonder weapons in small quantities to counter Russians reminds me of German "Wunderwaffe" from ww2, Tigers, Panthers, Me-262, 88mm guns etc...... that despite quality advantage and destroying huge numbers of Russian armor and troops, simply couldn't stem the tide and incredible numerical advantage.
Their hope is to bloody Russians as much as they can, but any counter-offensive to retake lost territories, i simply don't see how, beside total Russian collapse.
But yeah, as you say, pulling Russians into urban combat where their artillery and air advantage cannot come in play, is best what Ukrainians can do, though no doubt it cost them massively too, Zelensky said few days ago, that every day Ukrainians lose 100 dead and around 550-600 wounded.