Johnston, 27, has spent the last two seasons in Europe, primarily in the Swedish Hockey League. He tallied three goals and 19 assists in 50 games with Mora IK in 2018-19.
A native of Sudbury, Ont., Johnston played three seasons at Colgate University before spending two seasons in the Montreal Canadiens organization. He notched five goals and 25 assists for 30 points in 87 AHL games with the St. John’s IceCaps, and also skated in 10 NHL contests with Montreal.
Kapla, 24, totaled two goals and 22 assists for 24 points in 66 AHL games between Binghamton and Iowa last season, his second pro campaign.
Kapla, who skated in five NHL games with New Jersey following his senior season at UMass-Lowell in 2016-17, has appeared in 129 career AHL contests, recording seven goals and 38 assists for 45 points.