is it possible to mine cryptonight-heavy with Claymore miner ?
Try SRBMiner. For my Asus RX560 2Gb DualFan for cn/cn-v7 with Claymore - 495 h/s, with SRBMiner 515 h/s. For ch-heavy 325 h/s.SRBMiner 1.5.0
GPU1-3 - Asus RX 560 2Gb DualFan, GPU4 - Sapphire RX 560 4gb Nitro
Does SRB work with old cards like R9 390?
yes, even the much older R9 290x could run it
https://bitcointalk.org/index.php?topic=3167363.msg34331694#msg34331694